Not attempting whatsoever to jack the thread...
I have camped a fair bit, not a ton, but more than most and I don't get the "fly option" at all. Even midrange priced backpacking-grade tents are just not that heavy and setup is 1-3 minutes.
But most importantly, I don't need a shelter for the nice days, I need it for the crap weather. You know, those days and nights when camping kinda sucks or worse it is on the verge of dangerous. Give me a tent for snow, heavy wind, bugs, driving rain, hail etc. I will carry the extra pound or two gladly to seal out the mess.
FWIW I have backpacked camped for weeks in CO, AK, MT, and the boundary waters in CA. Like I said, not a ton, but enough to have been out in some real garbage weather with some real ridiculous bugs.
I don't know how you can make the assessment from home before hand or even from the bush that night whether you will need more protection throughout the night.
In rereading this, it may be a little harsh, but I really don't understand the tradeoff or the value of a tarp (or similar unsealed shelter) versus a tent.