They are convenient, but a tent, especially for sleeping, has advantages.
Privacy – You aren’t a stuffed sardine when it gets crowded.
Warmth – A tent with a rainfly is warmer than an open shelter.
Better Sleep – You are not poked, or kicked, or outsnored.
No Mice – Those critters can drive you nuts!
So why choose a shelter to sleep in?
Convenience – Less hassle. No need to unpack and set up a tent; no need to dismantle and re-pack the tent in the morning, possibly in the rain.
Clothesline – Many shelters have them already. Easy to rig up, or simply hang garments from nails and hooks provided. Clothes are protected from outside weather.
Ease – Can sit and lean against a wall to read, journal, contemplate (I’m sore, I’m tired, I wish I had a pizza and beer.)