Ha, ha. Mostly, because the hot air is escaping all the time.
It *is* a PITA on longer trips. I use an old (origonal) NeoAir medium. Blowing it up every night, then emptying it out every morn are painfully boring. In all cases it takes about 2 minutes to get it out, unroll it and blow it up. Or, crack the valve, let it go flat, then go take a pee in the morning...a minute seems like a half hour. Bad? No, I still use my NeoAir, but it *is* anoying. After 2-3 weeks it gets old.
For about 5-6 years before they released the NeoAir, I used the NightLite, cut down to 5 - 10.25" sections or ~52". This worked OK for sleeping on the ground, but, my bones started complaining about the shelter floors. I still use this on backwoods trips, where shelters are not usually found.
About that time I was trying quilts. I found them to be very drafty, mostly because the pad was not adequate to completely cover the ground. Old GVP style was to use your pack as part of the padding, the but/torso pad for the rest, with a seperate pillow. A bag was needed to make this work. With the NeoAir, you can slip your feet inside the quilt, wrapping it around the rest, pretty much stopping most of the cold drafts. But, YOU NEED A GOOD PAD. Theory dictates that your ground insulation (compressed in a bag, non-existant in a quilt) mostly comes from your pad. For three seasons, you need about an R2.5-R4 below you. On a hard floor, I need about 1-1/2" of cushion. In winter, you need about an R5 or a bit more. If you use a quilt, you need a pad that will stop drafts the full length of your body. The Neoair has horizontal baffles that can let in drafts with a quilt and is not my first choice for a winter pad. It only has an R2.5 or a bit more anyway, soo, it is not my first choice for winter pad. It works well for three seasons or 4 seasons with a bag and ground cloth.
Before I had the NightLite, I used the old GuideLite. It worked OK for stuff, but was heavy at 2 pounds. Before that it was the old military pads...wider at 24" but only a 1/2" thick at 28oz. Before that was the old rubber pads, quite heavy at 2.5pounds for 60". Several others were used with no real savings, too thin, too much heat loss, or something.
The success of a quilt is dependent on the type of pad coupled with it, in my opinion. (If you toss and turn, it might never work well for you, but I am ignoring that.) To me, you cannot mention a sleep system, without also mentioning the pad and head covering you use. For example: A 30z quilt coupled with a BA pad that weighs 1#11 and a balaclava that weighs 2.3oz is not all that great. A VersaLite at 2#2 and a neoair at 13oz would be a better choice for carry weight down to about 20F. So, it depends on what your system is and how you plan on using it.