As someone who spent the better part of two decades at a carrier (I joined as an acqui-hire to build an ISP), I've always been fascinated by the amount of crap carriers insist on having pre-loaded (and kept working) in device firmwares.

Carriers want (demand, even) that their online portals, customer support apps and (most importantly) ringtone shops be pre-loaded on devices, and have always tied that to critical firmware drops for network defaults, radio compatibility testing, and a lot of other (truly critical) functionality that only actually exists on the device's radio baseband and has zero to do with the handset OS these days.

Source: I was one of the program managers for the flying circus that was Vodafone 360, when we tried to work with Samsung to build a vertically integrated handset like the iPhone. This sank (mercifully) without a trace, and to this day I summarise what happened by explaining that Samsung actually had two engineering v-teams: the Galaxy team and... everyone else.

And we got everyone else. It doesn't excuse a lot of what was decided, but it was instrumental in killing the service.