What if Base Stats were lower, Scaling was higher and passive Gold Income was much higher?
League has this problem of everyone building mostly tank in order to out-damage the champs that only build damage. That works because bruisers and mages have absolutely massive base damage when ADCs generally don't.
Riot made it this way to "prevent snowballing." That isn't quite fair. If someone adc works her ass off to get fed, she shouldn't lose the late game just because you have your Annie main on the other team barely reaching 200 AP and still managing to instakill you with one combo of hers.
If Riot combated snowballing by instead of making damage items less useful, but gave everyone a better chance at being able to choose the items they want, those putrid Mage/Bruiser mains would actually have to start building damage in order to actually do damage, and tanks would have to rely on actual damage-doers instead of using their own heap-loads of base damage to do the job.