If you're someone that sucks at every champion and thinks if you play someone that people hate you'll get better, but then the ADC knows how to kite.
If you're someone with either insane skill or doesn't know how to use her passive.
If you're a dedicated main.
If you are weird and actually have a lot of success with this.
If you want people to hate you.
See Ekko.
If it's your first time playing the game.
See Ekko.
If you want to be extremely annoying.
See Ekko.
If you want to get a double kill whenever the jungler ganks you.
If you want to lose
If all of a sudden you're a yorick main that has mastery 7
go with full tank 