The BCM283x series has a good mix of features, but it is far from being the only solution for set-top boxes.
For example, if you want a full-featured chip for building an AP, there's maybe three companies capable of giving you one - Atheros, BCM, and Marvell. And that last only sells to Cisco. So you're stuck between two companies with drivers that are awful in slightly different ways, and only a year into working with one or the other do you discover the firmware bugs.
If you want previous-generation-equivalent chips there are more suppliers available, and some of them probably have decent drivers, but they're uncommon in developed-country markets.
Price, performance, availability, driver quality, etc may look competitive to the competition and affect a few million users.
If you sell a few million of these, saving 5 cents on the Wifi chip pays at least for 2 engineers full-time to deal with whatever issues Broadcom gives you.
It may still make sense if the maintenance burden is high and upstreaming has benefits, but that's not always the case.