I post on that sub pretty regularly. I actually find it to be one of the nicest communities on reddit and engaging with the people there in discussion about keyboards is fun.

I bought one for work, built one for fun/learning, and did buy nice keycaps for each. I get why the aesthetics of the keycaps and the switches/different form-factors appeal to people. Building and programming a keyboard is a fun project to do.

In the end, though, it's a keyboard, a utilitarian thing. I personally don't feel the need to collect them or invest in buying more of them than necessary. I don't want to switch out what keyboard I'm typing on often, or replace keycaps all the time. Every now and then to change up the look, sure, but not often.

But I get why people do.

They're interesting pieces of tech that are pretty easily accessible to the DIYer/enthusiast and offer a lot of options. I think the people who are really into collecting them aren't just buying a bunch of stock keyboards. They're building them, or mixing keycap sets, or buying/making custom caps, etc. If you're the type to want to tinker, mechanical keyboards offer a wide range of options for tinkering.

In that sense, you can think of it along the same lines and building custom PCs and case modding and all of that. You can design/create exactly what you want and have it meet both your technical needs and aesthetic desires. It's a form of self-expression artistically and you can create some nice typing experiences, and if you're so inclined, learn a bit about electronics and programming.

I like/enjoy/appreciate all of those things. It's just too expensive as a hobby for me to rationally keep investing money into when I don't have a practical need for that many keyboards. In general, I don't care to have more of a thing than I need.