The main problem is that they aren't comfortable to every head out of the box. They may never be able to achieve that. But third party comfort mods can take any headset to 8+ hours of perfect comfort for 99+% of people. And once you find out what works for your head personally, you can make all your future headsets just as comfortable first try. But the first time, you might have to try a few different options.

The VR communities have guides for how to try out a home-made free version of each type of comfort mod so you can more confidently purchase a more professionally made version. But even with that, I can see it being a sticking point. All we can hope is that 10 years from now, buying mods for your headset on day 1 is as normal as buying phone accessories day 1 with a new phone. And you can just ask your neighbor about what mods are good instead of the weird nerd in your life. Also, if you don't have a weird nerd in your life, that is step 1 to making sure you'll be ready for new tech early enough to benefit from seeming like you know what you are doing by the time everyone else finally gets on board.

It doesn't sit around if you find out about certain applications ... cough cough Virt-a-Mate

edit: downvote me haters, your loss

There's new content coming out all the time.