Why isn't it possible to lose mastery points?

Why is is that mastery points are still rewarded for poor performance? Sure everybody has bad games, but too often do I run into an Ahri mid lane who can't land a charm for her life, who consistently ults and even flashes into one of my teammates or I and still misses, or pops their ult immediately when there's a threat making it easy to take them down once they've used up their charges, and who clearly has no idea how to play Ahri. I'm tired of running into Yasuo players who only know how to chase people with their E and constantly push and never use their wind wall, or juke, or in the worst cases, barely even be able to land Q, then checking their profile after the game and finding them with over 100k mastery points. Sometimes I cry and pray for those who must have had to play on the same team as these people in the hundreds or even thousands of games of missed skillshots and cringeworthy failed plays and botched mechanics these level 5 players must have fed in to reach such a high level on a champion they obviously have no clue how to use. I feel like having level 5 is such a farce because you can't lose mastery points for doing a terrible job. Again, everybody has bad games, and that's OK. But I fully advocate having the system take away even a small amount of points for bad games because if the player really deserves their mastery level, the gains will easily outpace those losses. If some feeder just stubbornly continues playing a champion and ruins the majority of those hundreds of games for their teammates, then their mastery will actually reflect that. tl;dr everybody is feed, an unreasonably angry guy who can't feel pride in his level 5s that may as well be meaningless.