It's up to the brewer to make beer with the equipment he wants. A guy brewing his first beer on a bells and whistles-system will not be able to "out-brew" a seasoned brewer with experience and knowledge, which brews in a bag.
It's just how one wants to brew. I built my latest system with one thing in mind, eliminate as much "work" as possible with consistent results, because I find it fun to brew the same beers over and over again and adjusting. I can leave the mash and I know it does the same thing if I brew the same beer twice, so thats one variable I don't have to think about.
I bet I could bang out some decent beers on a BIAB kettle but I don't want to lift any grainbag, checking temps manually, step mash by adding water or fire the burner and and have to watch it as the temp rises etc. I just want to leave it and do something else if I'd want, then come back to mash-out.
That's why I have a HERMS even though a simple no whistles system can probably bang out the same quality of beer, but through a different process.