Yes, that really bugs me. I go to the ATG theatres around south London a fair bit, and there's no chance of persuading friends to venture that far south, so it's single seats or nothing. Sadler's Wells (I go to a lot of dance) is also irritating, at least if you buy the slightly restricted view seats on the side of the front of the second circle.
Speaking as someone who has just dumped Tastecard because I can rarely use it for the 50% off pre-theatre because so many venues only offer 2-4-1, I totally agree with you. It's single-ist!
Agree that interval-killing can be tiresome when you're on your own. Fortunately, when I go to dance events it's pretty rare that I don't spot other people I know during the interval, so I can talk to them.
Good tip, thanks!
Also agree about the hassle of trying to coordinate if you're going with other people. It's happened so often over the years that a friend has said "We must go and see X" and we end up running out of time because we can't coordinate our diaries that now I get a bit more callous and go on my own if necessary. It also leaves me free to make a last-minute decision about something.