Exactly. Now that the catapults work castles are too easy to take, sometimes the attackers even get a positive k/d which is plain ridiculous. A default healing tent for all castle defences would add at least some balance, + it would also add at least some dynamics for melee defenders who otherwise have to either stay behind the walls for half an hour or jump out and die like idiots. "Get shot - run to the tent" is at least slightly better than "jump out- waste a ticket, wait a bit, repeat" or "elevator music....... 10-15 minutes and they're gonna charge".
It;s also somewhat realistic because any besieged castle /town used to have population which helped the men fighting on the walls, including treating the wounds .