Comment by Silhouette

Some developers also take an active interest in the design and feature set of the product they're developing. IME those developers can often produce good results once a general direction is set if they have access to real users to collect feedback. But it's important to recognise that these are essentially two completely distinct skill sets and mindsets and it just happens that some people have both.

It's not really any different to the old arguments when continuing a career beyond senior dev level meant moving into management but there was no guarantee that just because someone had been a competent developer they would also be any good at managing anything. Some were and produced great results - in some cases informed by their understanding as former developers about what would be possible and what it would realistically cost - but in other cases the Peter Principle hit early.