Been reading a lot of threads about people who buy a house with a pool that "hadn't been touched in years". The pools are predictably mucky, green, disgusting, etc. People go on to SLAM their pools, and it takes usually a couple of weeks and everything is perfect. However, I had a dumb question. When faced with such a gross looking pool, why don't people simply drain/refill? Why go through all the work & hassle of buying/transporting dozens of gallons of bleach, sweeping/vacuuming multiple times a day, raking stuff out of the pool with a skimmer, etc? Is it about saving cost of the fill water and chemicals to re-balance, or is there another reason?