Economics. If you only view flights as getting from point A to point B, then the rewards programs aren't worth it. For some people, there's more at stake than getting from point A to point B... eventually.

Comfort and less time wasted are very valuable for the wealthy (in terms of $ they're willing to spend without monetary return, since it ends up being a smaller percentage of their disposable income).

For business travellers, it's efficiency, fewer missed meetings, and psychological comfort, allowing maximum focus on business concerns.