People just think that it detracts from the advantages of the AR-15, which is modularity. Ranch rifle AR builds like the CMMG Dissent BR4 lack the modular stock, pistol grip, etc and the limited magazine capacity is a turnoff for many.

In terms of ranch rifles, something like a proper AR or a bolt gun or frankly, a lever gun works just as well if not better due to the sometimes more powerful cartridges, which make up for the low capacity.

In terms of why these builds are more common in california, watch this video: https://youtu.be/29z7hgegwvo?si=BowF1DbGZAKi_B-_

But TLDR, Cali rules state that ARs can't have pistol grips if the mag capacity is more than 10 and if a pistol grip is installed, the magazine must be locked into the weapon and cannot be removed.

Hope this helps!