Why do criticals exist

So marksman champions can be played. (Except Vayne of course)

Would you look at that, a dumb question!!!

I dont mind criticals, however they shouldnt be random. I like Ashe's Crit mechanism, and i think all ADCs and some assassins/bruisers should gain champion-unique crit mechanisms. Example, make Caitlyn's Headshot passive a 1/7 attack a crit with enormous damage that scales with crit chance.

According to Riot it's so when an adc gets ahead of another adc, such as a finished IE against a BF+Pick Axe for example, the one without the IE could still win if their opponent doesn't crit, as if it was a damage amp. as people suggest, the person with IE would win 100% of the time. Which makes somewhat sense until you look at someone like Tryn who gets it as his passive starting at level 1 and easily wins the lane purely off the rng from it.

My biggest issue with crits are assassins who build just something like ghost blade and randomly crit you back to back for 100% of your HP, such as Rengar jumping from stealth and crits you for 1.2k+ then crits again.