I'm of a similar philosophy, but also because I'm not beholden to rushing a minimally viable product to the feet of some angel investors (Super allergic to that after a few experiences). I mean it's kind a a premature optimization if you just need to get a working example out there for people who like to see fast results, but if you've got the funding to start your own company just writing it properly for performance from the get go is the obvious thing to do.
I also choose a stack like that because it's what I've been mostly working in for a long while now and it's really productive (For me).
yeah, I get the same - I'm probably not going to get something up as fast as I would if I used Rails (though it's probably close - I've built so many sites on this stack that I know all the pitfalls and have a lot of the boilerplate down to copypasta now).
But this backbone can take a lot of experimenting with features easily, and is fast enough to forgive a lot of sins - I generally just don't have to worry/think about performance at all.
I also choose a stack like that because it's what I've been mostly working in for a long while now and it's really productive (For me).