I've noticed a couple of bug fixes that were in Windows 10 insider builds were recently touted as Windows 11 exclusive improvements. So if one of those bugs affect you, that's a reason.

Otherwise, it's the same as it always is: new software or new modes for software will increasingly become incompatible with Windows 10 and earlier over the next few years. Some future directx feature will be win11 exclusive and will be critical to performance sooner or later.