Pashute,
Yes, there are valid reasons for some people not to sleep in the sukka if it won’t be taishvu k’ein taduru due to the cold, being in an unsafe neighborood, not being with the wife etc – each person should ask their rov.
But that’s not what I was talking about. By Lubavitch, even bochurim in warm climates in safe neighborhoods do not sleep in the sukka. The reason I have heard (and if anyone knows differently please tell me) is that the rebbe said the shechina is in the sukka and its painful to sleep there so its not teishvu k’ein taduru. And if you are not pained by sleeping where the shechina is because you are not on such a high madreiga, then that itself is painful and therefore its not k’ain taduru. The problem with that reasoning is that this would be a reason for every yid in every generation in every climate not to sleep in the sukka. So why did chazal in mesechta sukka talk about sleeping in the sukka?????