What if Crit was only half as likely to work?

So i been thinking about this for a while, and i keep coming back to one thing. "Why is crit chance so high?" I love the idea of landing a clutch critical and changing the course of a fight. I love the idea of ADC's building it and having it help with the DPS and siege power. I HATE that it's so easy to get so much of it. i can drop 8600 gold and buy + + , 80% chance to do 250% damage and a ton of bonus attack speed to make sure that i land quite a few in a short period of time. Now imagine for a second if that same investment only gave me 40% crit chance? If i land a crit i still hit like a run away semi truck, BUT i have a much lower chance of doing that. Sure if i get super lucky i could still land 4 crits in a row and melt all but the tanky of tanky targets. But more likely i only land 1 maybe 2 of those. Players can now react to the ADC, which means that they have to be protected more. A protected ADC is still going to melt faces, but an unprotected one is not going to have the security of doing 500 damage per attack while also attacking about 2 times per second, or in other words "i'm safe because my damage output kills anything coming at me"