Renting kind of falls under the coupon theory. You can keep your MSRP inflated and sell to the uninformed at high prices, while also capturing that segment of the market that will only pay discounted rates.
Renting essentially gets you a deluxe room at a slightly higher than moderate price. And human nature is that once someone has a taste for the sweet life (or suite life...haha), it is VERY hard to go backwards.
I can attest firsthand. That first "free" upgrade I got to a first class seat 10 years ago has cost me dearly. I don't upgrade all the time by any stretch -- but I spend way too much time and airline miles figuring out ways to get there.