Some developers just don't care. JBL, for example, has a "JBL Music" app that's needed to configure their L8 and L16 speakers. These are expensive speakers! Yet they didn't update the app for iOS 11 so people who upgraded and don't have an older device to fall back on can't configure their speakers anymore.
It's maddening; the beta period runs for months and you even TELL these companies their stuff is broken yet they don't fix it.
Most of these types of decisions are Management, not developers. JBL probably contracted for the original app, did not have a lot of users, and the original contractor probably priced the revisions too high for management.
[doublepost=1506721133][/doublepost]In all fairness to these companies, I can tell you why we don't do anything with Apple betas. Apple arbitrarily removes and adds features in the GM or release that are not in the betas. No warning, no reason, no strategy, they just do, and often without mentioning anything in the release notes.
For example with High Sierra, they removed the apple file systems from devices with fusion drives, which are all current iMacs. They did not wait to get it right, or apply pressure to get it right, or add resources to get it right, they just yanked it.
The reason developers don't take Apple upgrades seriously prior to release, is simply because Apple does not take developers seriously prior to release.