I don't bother with a tent because it's too much weight and bulk. If I had to sleep on a frozen mountain slope in the midst of winter I'd sure bring a decent tent. For anything else, a tarp is more versatile and lighter, though admittedly not as warm per se.

Most of the time I actually sleep under my poncho. This is probably the most economical kind of "serious" outdoor shelter. I always carry my poncho as my primary rain gear so I might as well use it to make a shelter. It's really useful for that sort of thing.

Also, I find tents a bit claustrophobic (I prefer to be able to see what's going on around me) and too prone to damage. Way too easy to snag your tent on a stick or rock. Making a fire anywhere remotely close to a tent is a bad idea too, hot sparks will burn neat holes and turn your prized tent into Swiss cheese.

A tarp/poncho setup is somewhat more practical IME. If warmth is a consideration, you can make a lean-to with 3 sides closed and the 4th close to the fire. Very likely warmer than an ordinary tent. The smoke will also keep away mosquitoes, insects and whatnot better than anything else. BTW, Les Stroud does pretty much the same thing on most of his shows though he tends to make fire VERY close to the shelter. I tend to keep it slightly further away but still within reach.

YMMV.