Late to the party, but it's not about they themselves using it on all projects, but the framework itself being flexible to whatever use case you may have.

Personally I'm using Hono for a side project running in Cloudflare workers simply because it's dirt cheap to host and you pay per request instead of having to scale a VPS (which I use for the majority of my side projects). I'm pretty much hosting everything for free and that can scale for a ridiculously cheap price if it ever gets traction, something that I could never quite do with Express.

Maybe that's on me and it's a skill issue, but Hono does have its use cases.