I think the problem with btrfs is that it entered the spotlight way to early. With Wayland there was time to work on a lot of the kinks before everyone started seriously switching.
On btrfs a bunch of people switched blindly and then lost data. This caused many to have a bad impression of btrfs. These days it is significantly better but because there was so much fear there is less attention paid to it and it is less widely used.
I think the main difference is that while a graphical session can work through some issurs, a file system is not allowed to fail under any circumstances. The bar is way higher and stability a lot more important.