I'm sure a lot of it is to tempt you in by staying at the hotel in queston to enjoy your meal etc.
Same with supermarkets. Sell something cheaply, you go in to buy it and end up spending loads of $$$ on other things.
It's taken me a week to get around 5500 points and that's from playing now and again.
Not being that local to LV, I would end up staying a few nights so if I were to get a one night redemption at say the Bellagio, I would most probably end up staying there for a couple more paid nights because of that, spend in their casino etc.