Serious question about minions

What is the positive impact of minion block in league of legends?

Every time I have ever witnessed someone get minion blocked, the only reaction is frustration and annoyance. Personally, I've considered quitting forever after particularly frustrating minion blocks. Even if I kill someone who was minion blocked, the achievement feels half-ass, like they got screwed out of a fair fight.

Why would Riot continue to keep one of the most annoying, pointless, buggy, etc mechanics in this game???