I'd say comparing hardware vs software is very different. If there were 5+ competing OS's with decent market share, maybe you'd have a point there. But the reality is that mobile software is controlled by 2 trillionaire tech companies that made use of anti-competitive measures to prevent consumer alternatives.

Heck maybe even 3. The desktop scene doesn't feel that much better, but them all allowing "sideloading" as we call it today alleviates full control of the OS.