My experience is about 50/50 for receiving the extras with motherboards, and also for receiving good motherboards.
In fact, the mobo I have in this machine right now is a newegg refurb.
I think if you receive one without any extras, it's likely because the previous owner "forgot" to include them when they sent it back to Newegg.
One bit of advice I have is, if you get a bad or dead refurb from newegg, do an rma repair, versus refund. If they have another refurb of that model, they'll send you that. Most likely, they'll state that they don't have a replacement, and issue a 100% refund. Yeah, it's playing their own rules against them, but I don't believe in having to pay a 15% restocking fee on a dead component that they haven't tested.