The point is that viewers and streamers does not directly or even indirectly correlate to people abandoning the game because they cannot play a specific hero. If this were a reason they would quit then most would have done so already due to hero limits.
They already encounter situations where they cannot play their hero. Yet they are still here. Hero bans would not increase this by much.
Citation needed. I don’t believe this at all beyond a short term result at worst. The long term result for them would be of multiple hero proficiency.