My ds does occasional boarding because I am a single mum, working full time, and if I get stuck behind a points failure or a cancelled flight or a closed motorway, I can call the school, and they take over, he has his supper at the boarding house, stays the night if necessary.
When I needed a cancer op, I could book DS in for three nights and he has a home-from-home where he is well cared for, relaxed, well fed, surrounded by friends, gets his prep finished etc.
Given my ex's refusal to take any part in the care of his ds, I needed a reliable partner who would help when necessary. The school provides that. Without the option to board, I'd have to give up my job, couldn't pay the mortgage, etc etc.
Our House mistress is wonderful. She never says no, (although I don't abuse her kindness.) She and the other staff are infinitely more reliable and competent than a husband.