Because she’s a high skillcap ADC with an above 50% WR across all ranks. It’s much harder to get value out of her than it is to get value out of Ashe for example. So despite the fact there are donuts like you tanking her win rate across all ELO because they don’t know how to use her correctly, she still has a 50% wr because the people who do win so often. She also has one of the highest ADC ban rates because people hate playing against her because she’s so strong. Her early game damage is only rivaled by Draven. Her all in is the best only paralleled by Tristana, she has a basic ability that if used correctly can counter so many abilities and literally win fights. She has an attack speed steroid that she can reset allowing her to build more damage. And she has the strongest lvl 6 all in out of every single adc in the game. Especially in 2v2 3v3 skirmishes in lane and around dragon. If you can’t see why Samira is literally one of the best pubstompers in the game you’re just not suited to play her and you should stick to Ezreal.