Because the developers are the ones that get the betas. And they're letting too much slide. Like what you just said about lag. You can't address it. But people notice everything. That's why I made this thread.
I mean the iOS 10.1 beta 2 I'm using right now introduces a new bug where you can't even swipe to delete in iMessage.
I mean... ¯\(°_O)
Let me ask you a simple question:
When you go fishing, do you catch every fish in the lake?
iOS is quite complex. So much so that, if Apple held into it until they've investigated every possible scenario, beta testers wouldn't get their hands on it for years. If the beta testers held onto it until every possible scenario was tested, you'd be complaining that updates take too long to receive.
For what iOS is, and as big as it is, I feel it is high quality - the last bug I actually experienced was Safari crashing and I believe that was in iOS 7.
If you're unhappy with it, perhaps your time would be better spent switching platforms instead of wasting time complaining here - which actually serves no purpose. Focus on what matters, not what angers.
If you really want to fix the problem, learn how to code and get a job at Apple.. and then see how easy it is to release bug-free software.