do I have to ask you to be on time every day?
if the job has regular hours, you should tell people that. if it doesn't, then it shouldn't matter. i've had jobs of each type and it was a single sentence with no further conversation required. it's also not something a person can just know, so this is a bad example. side note: being 'on time' has never been a thing at any of the companies i've worked at and i don't have any concept of that at my company either.
meetings are the only things that i've ever been part of that needed to start on time, and i agree people should show up on time for them. if i have an employee who is habitually more than trivially late to meetings, i'll mention it to them and that fixes the issue 99% of the time. honestly, though, if this is something that gets your panties in a bunch, you may need to relax a little. i give my employees all kinds of latitude because trivial issues like this are meaningless in the grand scheme of things. i actually like if people are late because they were working; it tells me they're focused and the meeting is interrupting them, which is incentive to not waste time in meetings. i bill my clients based on my employees' timesheets, so meetings hurt, but it's not worth making a fuss over a few minutes. the chit chat that happens during that time helps reduce pressure and stress on top of fostering relationships.
Do I have to ask you to keep your desk clean?
if you're controlling, i guess you do. i keep mine clean anyway, but why do i care if one of my employees has a messy desk as long as they get their job done? then again, i'm not a micromanager. this also feels like a bad example because they may organize their desk and you still may not like it, but none of that has any bearing on their ability to do their job.
What else do I have to ask?
anything you'd like know and anything you'd like them to do would be a good start. this has very little to do with how a person dresses in my experience because you should talk about things that are important to you. how they respond should be the real data, not how you interpret things based on inference.
i've apparently taken huge risks by hiring people who didn't buy expensive clothes for a single conversation. the ones who did need to wear nice clothes were told they'd have face to face meetings with clients and business or business casual attire would be required. i tell my employees to dress comfortably in the office and they can interpret that as they see fit as long as it's not ridiculous or over the line in some way. i've never had a problem.
It is trivial to dress nice to an interview. If you can't do that, why should I believe you can do everything else?
that is, in fact, the entire point of the questions you should be asking them. if the job is to look nice and show the face of the company to clients without much other substance, then i guess you can judge them by their appearance alone. when i ask people to tell me all of the gotchas they're likely to experience when designing a 10 Gbps amplifier on a 22 nm process and they get most of it right, i don't care if they have nice shoes on or not because the job is about designing amplifiers, which can be done in slippers. if they need to talk about the design with the client, i'll say that and they get it. i assume the people i'm interviewing aren't stupid, so maybe we just have a different outlook.
I'm hiring someone not only that can do the job at hand development wise, but also navigate handling clients and representing the company.
that should be in the job description. if it is and they don't understand the expectations, then how they dress may be more of an insight, but i still wouldn't rule them out if they handled themselves well. representation and client relations are a huge part of my business, but i don't expect to hire someone and just let them go meet clients without any training. saying a single sentence about what i expect them to look like when meeting a client is hardly a big deal and then there are zero miscommunications. the rest of the training is about how i run my company and how they should reflect that. what clothing should be worn fits into that conversation naturally and my lawyer even recommended it because it protects me in many ways. i also use this as an opportunity to score points with my employees and earn their trust because i let them know if that's a problem to come see me and i will make any necessary accommodations, which means i'll buy them stuff if they can't afford it since i asked them to dress up. i pay my people well, so this has never been an issue anyway.
Asking someone "would you do x in y" is a lot less telling than someone doing x in expectation of y already.
that's true in some circumstances, but how they dress to meet me isn't automatically how they'll dress to meet my client. you've picked a single thing that you expected them to do and overlooked a billion other things that could also be expected. i've heard of people ending interviews early because a person didn't sit down from the right side of the chair or they ordered their food incorrectly or any other equally retarded reason. basing their intelligence and general utility on what they wear doesn't seem very different to me. i know you probably justify it by saying they don't have enough forethought or they don't have enough common sense, but my experience says that's not actually true.
judging a book by its cover isn't always wrong, but you're talking about a person that can be trained and is probably adaptable. maybe they are willing to do what it takes as long as they understand what you want. just because they didn't nail your entire list of needs without ever talking to you doesn't mean they're substandard.
i've hired people who turned out to be very thoughtful and conscientious employees without needing me to intervene and they weren't wearing expensive suits during the interview. it's too simple of a thing to use as an indicator of everything else.