I don't think that's at all what consumers care about. Cell phones need to be approved by the carrier to even run on the network, and of those approved only a small subset is sold and subsidized by the carrier. Combine that with the small number of carriers allowed to operate in most regions, and you end up with a very limited number of products that the hobbled market can support, regardless of the volume. The real market is between the manufacturers and the carriers, not the manufacturers and end users.

There's all sorts of crazy tablets, laptops, and handheld computers at any given time, but even large conglomerates struggle to keep their phones available through cellular carriers.

Meanwhile, companies that are very successful with stagnant and feature-limited cellphone designs have to put much more effort into computers and tablets to get a reasonably market share. Apple kept lightning ports on their cellphones long after their tablets supported USB-C, despite effectively being the same hardware, sans cellular modem.