It is stipulated in his contract to appear at specific promotional events in the run up to UFC events. McGregor's problem is that he makes it all about him, had no problem doing so when he was knocking lumps out of the little guys in the featherweight division, but when he gets given the chance to move up weight divisions, he ends up losing. Now that he's lost, he suddenly doesn't want to commit to the contract he agreed to and signed, but instead wants special treatment, and uses the income he's generated for the UFC as leeway, disregarding the money the UFC had made for him in the process.
The thing is, if you make yourself the biggest draw, talk yourself up (and mostly back it up as well), then it's no use suddenly throwing the toys out the pram when it does end up being all about you, all because you got choked out in your last fight which was a fight you demanded, a fight you predicted you'd win in the 1st Round, and a fight that ended up showing you up.
I'd be surprised if he fights at UFC 200. White and the UFC never back down from fighter demands, and to do so now would show that it is McGregor with the power, as opposed to the company.
White even offered to fly McGregor's entire team out first class from Iceland, and to fly his entire gym - every single piece of equipment - to LA, have it set up identically, and have it ready to go from the moment he set foot on US soil. Not only that, he offered a private jet to take McGregor to every single media commitment FFS. No other fighter gets that treatment, and McGregor turned it down.
Only one at fault here is McGregor. I like him, but it's also easy to see why folk don't. The two things to take from all of this are how rattled he was after Diaz took all his big punches, then sent him spinning with one, before he got choked out in fairly easy fashion, and secondly, of how rattled he still is, even going to these extreme lengths to try and gain extra training and special treatment.