I personally prefer keybase but to each their own. UX matters to most people and there is no obvious solution here that I could recommend to people that are less technically savvy than the typical HN commenter.
For more critical things, legal requirements are higher, and often aren't met by these services. E.g. in Germany (although the digital part is EU level standards), some things either require ink on paper or what's called a "qualified digital signature", i.e. a cryptographic signature, signed with a key that an officially registered CA has provided a certificate for, after verifying the owners identity. That's more process to properly meet (you need to be registered, do ID verification to spec, have requirements on bookkeeping and auditing, ...), and people have fallen into the trap of not using it were required.
E.g. a delivery service here was recently in the news because they had used a "draw on screen" signature with Docusign for work contracts - which meant the contracts they had intended to be limited-term contracts actually were contracts without end date.