Business travel. Company or client says "use Marriotts, we have a corp discount." Whether the corp discount is actually any good or whether there are better/cheaper hotels nearby often doesn't matter - you're still expected to use the chosen brand.

In that case, the points are essentially "free" to the traveler. You may be able to decline them and accept a trivial number of airline miles instead, although to be honest I'm not even sure this is an option. It's been 20+ years since I've handed a physical airline card to a hotel front desk clerk to get miles instead of points.

But certainly, for personal travel or cases where the guest has a lot of choices, points and elite benefits are just part of the overall value proposition.