Casino vs pool

I live out near a few casinos and one of them has this amazing pool area- a big lazy river with inner-tubes, 8ish hot tubs, tons of chairs-- it's all over the top nice. 

I went there the other night and I thought it was so interesting, you walk through a crowded casino- it's not ugly-- well lit, nice carpet, it smells like smoke, but still fairly okay. 

Then you walk outside, to this high resort quality pool area, and you see no one! I think we interacted with 5-6 other people here, in this huge place! 

I don't understand why people would choose to stay inside when they have this great place just a short hallway away. It's so foreign to me!