Because blizzard doesn't like when there's unintended mechanics that create a skill gap of any kind. It's why genji ledge dash was patched out early on and why stuff like rocket jumping is so braindead to execute compared to other games.
I agree with you though and don't know why blizzard goes out it's way to remove or water down advanced techniques when they're also pushing esports so hard at the same time. Casual players are barely going to notice such things (if at all), and great competitive players are still going to win regardless of how much you dumb it down (see: smash bros brawl), so all you're doing is making the game worse for the dedicated section of your fanbase that is mainly interested in improving.