I'm not quite an ultralighter, more just lightweight/superlight. I choose a solo tent for convenience and simplicity. There are many that pack small, utilize a connected pole system, and work as expected. I love getting to camp, laying out the tent on the matching footprint, throwing the pole in front of me and watching it assemble itself, clipping the tent to the pole, and putting your stuff inside. Throwing the fly on and staking in is fast, and I like the kind that is free-standing for the same reason. I have tried a few, but I now love the Fly Creek series from Big Agnes. So light, extremely durable and very waterproof/stormproof (first trip out was a crazy storm on mt marcy and it held up incredibly well with ZERO leakage.) Even when I woke up and discovered water running between a tarp I had sloppily set up as a footprint and the tent floor, the water never came through. That was a miracle.
I think that those who do longer distance through hiking and need to shave every ounce would be much happier in a tarp or tarp-tent setup. They are more versatile and can be pitched in less ideal situations. Plus if you're a really crazy ultralighter you use the tarp as a rain poncho as well! I just can't deal with mice, having to baby my tent, having to futz with the setup over and over to get it pitched right, and having to rely on the right pitching angles to avoid exposure, etc. Nothing like just zipping up a rain fly if it starts to rain, or if you don't want a breeze blowing over you. Also great to have a place to change when needed, and you can cram your girlfriend in if you need to.
Finally, there are many 1 person shelters that make superior winter tents - less open space to heat and a tighter, more enclosed space means more warmth. Also means you don't need a bivy, so when calculating weight, those with a one person tent can leave a bivy out of the equation. For example, I've weighed some tarp/bug screen layer/footprint/bivy setups at equal to or more than some of the lightest solo tents.