IMO, its because they promote mediocrity. When I go to the gym I push myself beyond my limits. That's the only way you see change. I don't go to the gym and read and watch TV on the treadmill. I'm there to work out.
If you look at many people who go to the gym you'll see that they want to stay within their comfort zone. They don't want to exert too much effort because it's too painful. I will guarantee you that if you followed these people throughout their life you'll see that they aren't risk taskers They live boring lives. You have to be willing to get out of your comfort zone to see change.
But how is this affecting you? If you let the people around you dictate how well you work out, would you not by your very own definition be part of the problem as you see it: 'everyone at the gym is lazy so I can't get a good workout'. Be part of the solution, not the problem man!
Unless you're one of those people that has to slam the weight and make animal noises with every rep than please stay at your better gym. I giggle every time I see a guy slamming a 50 pound tri extension like its 100+ pounds and even then. If I can control 135 after three sets of 12 if your having trouble with 50 lighten up untill you can control the weight. Or the dude racking a 135 pound bench with so much noise and fanfare after a set of 5 that you would wear you just witnessed a world record attempt. Or even worse the guy with the headphones in and is "singing" aloud while slamming out the noisiest 25 pound hammer curls ever witnessed. Is planet fitness the world's greatest gym, no. Is it worthy of the shit thrown at it, possibly if you ar talking about the corporate side. But from a 'is there enough here to get a solid workout in and build strength, stamina and or size, hell no. Learn your body and what you need to do to make it grow, and use the tools you have with proper form and you will grow. I have seen 2 IBF boxers and 3 MASSIVE body builders that others knew from turing at the PF my buddy goes to.
Never once was I asked to limit my weights on any of the machines, no one has bitched when I dropped a 75 pound DB on my 3rd set of 15, or has the lunk alarm went off after my WOOHOO!!! or Ya' BUDDY!!! after a PR. I even grunted a couple times on my last rep when upping my weight on the, gasp, smith machine bench press. Lighten up guys, and worry about your body and not those around you, unless you are so weak minded that you need to external stim to push yourself beyond where you are. Strength comes from within, to balim others for your failures or limitations is just lame.