This isn't about thunderbird specifically but I can't understand why companies keep making this mistake. They (1) mistake removing legitimately useful (sometime

This isn't about thunderbird specifically but I can't understand why companies keep making this mistake. They (1) mistake removing legitimately useful (sometimes even critical) features for "simplicity", and (2) copy their competitors, often badly. They also never seem to properly think out or test there changes first. Can't they understand that people will just use their competitors because they can no longer use their app thanks to (1) or because they no longer have a reason to (2). Mozilla fell for this. Gnome fell for this. Is it really all for the sake of maintainability? At what cost?! I just don't understand it. Can someone explain? Edit: Just looked at TFA. At least the author seems open to user suggestions and feedback. That's much more than what other projects are willing to do.