Why were towers changed to what they are now?

Towers, currently, are just about useless. Actually, they are useless. Incredibly useless. But it isn't really so much their damage (however low it is) but rather their survivability. As it stands, the out most towers have 20 armor and magic resistance when enemy minions are near by, 10 armor and magic resistance for inner towers, and zero armor and magic resistance for inhibitor and nexus turrets. First of all that should be the opposite of what it is, with outer towers having lower resistances that increases as you get in, and second of all REALLY? 20 armor and magic resistance is all you can muster for the most well armored towers Riot? 20? That stops just about nobody. A single wave of minions can deal up to two to three hundred damage to a tower with no distractions like other minions. (Cannon minion included.)

Please, do something about towers. Increasing their health doesn't help much at all, and only delays the inevitable when the real problems to tackle are their resistances.