For sure, the hard part isn't building it, it's getting people to actually use it. The amount of effort involved of actually acquiring and transporting a hardware security key is well beyond what most "normal" people are willing to do.
Plus, reading your example in a different comment, it's completely jarring to someone who isn't used to reading things in that format.
I get why everyday users don’t use it but why doesn’t an org like coinbase? Yes the quick and dirty poc I built in 5 minutes is a bit jarring but it could easily be adjusted so the beginning of the tweet reads like it normally would and the end is the cryptographic signature nearly separated from the main message.
Plus, reading your example in a different comment, it's completely jarring to someone who isn't used to reading things in that format.