I would say that their competitors have failed to provide a better alternative.
What's the point of buying an Android phone (from the average Joe perspective) if the OS is preloaded with bloat and the experience is a sluggish phone?
A power user can root, install a custom ROM, etc. But can your average Joe? Or wait... what if not even a power user can install a custom ROM because the poor wording behind a feature of your phone makes it look like your warranty is void? (fig [1]. Knox Warranty Void)