People use their pool much more if they also have a hot tub.  They tend to open their pools earlier and close them later in the season.  That’s largely because on those “iffy days” when it’s not quite hot enough to swim, they might use the pool anyway, knowing they can hop into a hot tub to warm up.

Also, it can offer adults a break from the kids, with the young ones in the pool, and adults in the hot tub or vice versa.  Of course, it’s wonderful to hear the sounds of children playing and having fun, but it’s sometimes best enjoyed at a bit of a distance, right?