it's about demand and economy mainly.

a full-size is still the most familiar layout for everyone. they have very affordable options, easy to obtain, and cover all sorts of needs. because of this, beginners will get exposed to this layout first. this creates sustainable demand. manufacturers can make a lot of them, without worrying about market demands (economy)

the reality is, only a very puny fraction of users decide to explore options other than full-size.

edit: in short, without sustainable demand and economy, it's not really viable for manufacturers to invest in making them.

The Leopold FC980 is a 1800 layout.
Keychron K4 is a 96% layout.

I don't like the 1800 layout much. For the sake of 3 inches table space, you need to live with a 1.75U right shift and 1U numpad zero. Might as well go full size unless you really really need that 3 inches.

im a big fan of 96 layout mkb, but not many choices. Those custom build models by China manufacturer are so much more expensive than ready build ones.
hi, do you know what is the closest gateron switches to cherry mx brown?

Using brother's cherry blue now, so heavy.

Best keycap compatibility would be handsdown the Magicforce 68 (even a standard 104 kit fits, last I checked), then the RK71, and lastly, the AK33 (coz those 1.25U keys all over the board isn't helping)

Can't really say about the "bang per buck" coz, they seemed to be wildly different in pricing with the MF68 being the most costly one, but it's also one of the "more decent without too much work" ones.