I am being sincere and a little self deprecating when I say: because I prefer Gen X-coded projects (Node, and Deno for that matter) to Gen Z-coded projects (Bun).
Bun being VC-backed allows me to fig-leaf that emotional preference with a rational facade.
I think I kind of get you, there's something I find off putting about Bun like it's a trendy ORM or front end framework where Node and Deno are trying to be the boring infrastructure a runtime should be.
Not to say Deno doesn't try, some of their marketing feels very "how do you do fellow kids" like they're trying to play the JS hype game but don't know how to.
Yes, that's it. I don't want a cute runtime, I want a boring and reliable one.
Deno has a cute mascot, but everything else about it says "trust me, I'm not exciting". Ryan Dahl himself also brings an "I've done his before" pedigree.