Pool lots are great for apartment-living Sims, Sims too poor to have their own pool, Sims who prefer to use their yard for some other purpose,... I have a teen Swim Team who meet at a public pool. Townies, including children, come swim there autonomously. I've got one indoor pool lot for that, plus I have a pool in the Oasis Springs park, along with some water slides and toddler play equipment - it's become very much a play park for all ages now (though it's not a pool lot).