Most hiking trails don’t provide shelters. The Appalachian Trail and The Long Trail (Vermont) have many shelters.
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.)
Camaraderie!
Ray Anderson 
A literal sardine story for you… once at a shelter on a snowy night, many hikers huddled into the shelter for warmth — who wants to pitch a tent in a snowstorm? About 12 of us were crowded in there. There was a bear line, luckily, because recent bears had been spotted. A girl in the shelter got comfy in her bag and then wanted a midnight snack. She opened a can of sardines. The smell was overwhelming. Sheesh. Even without bears around, don’t eat sardines in a shelter. Didn’t sleep a wink all night. I would generally choose a tent over a shelter any time, except in event of a snowstorm or hurricane.
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I also remember being stuck with a dozen others in a shelter during a snow storm. The place looked like a bomb had hit it. I didn’t get much sleep, but remember everyone talking about hot food like pizza and fries, etc. Glad no one had sardines!
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