Cost. I personally use them everywhere but that's because I hate wire nuts.

For DIY there is nothing better than Wago. I love them for semi-permanent stuff. Understand why pros might not want to spend several dollars per box on connectors but for small projects they are amazing.

As someone with a shaved head and greasy scalp I will often wipe down my head with a washcloth. Either right before bed or randomly if feeling gross. Probably won't help if he sweats in his sleep though.