CrunchyFritos I foresee this as being a feature I would want to use spontaneously—yes, I would set it up for Wikipedia and Reddit, but there are lots of other sites I only use occasionally that wouldn’t be worth the effort of setting something like this up (but using a “bong” would be quicker than typing out “site:something.com”).
On top of this, there’s the fact that I want to have the option of searching via Kagi or the website itself, and while it’s possible to set up custom bangs with different names for each of them (e.g. !r and !rkagi) that adds further complexity.