I honestly think it's a money thing. Imagine paying your lawn guy a years' salary up front. You're gonna ****** and moan about the blades of grass he missed with the mower, but you're not gonna complain because he shows up on schedule to cut your grass every week. At this point, you just wanna get your moneys-worth outta the guy until something better comes along.
It's simply a bean-counters mentality.