> standard traffic control at intersections would be unecessarily inefficient

It’s already unecessarily inefficient! I can’t count the number of times I’ve stopped at a red light and waited for 35 seconds with no cross traffic only to be allowed to cross just as a cohort of 50 vehicles has to transition from highway speed down to idle. So much fuel and time is wasted due to bad arbitration schemes!

This is why the UK prefers roundabouts where ever possible. They're much more efficient than a light-controlled junction, since anyone can go when ever there is any suitable gap at any entrance.

Not that we don't lose the plot sometimes too... there are plenty of light-controlled roundabouts near me. One has to wonder why.

The funniest one I’ve seen was in Lisbon. There’s a roundabout that has a light on the inside. Not to enter the roundabout! But once you are inside one, you must stop at some point.

Roundabouts are ideal when there's a single lane in each direction. Once you've got two or more lanes the roundabout requires crossing lanes on entry & exit if you're not in the outermost lane. That reduces the chance that there's a suitable gap at the entrance, lowering throughput.

Many times traffic lights are poorly designed, or have lost timing over the years and never been tuned back to correct, so you might be fully correct in your frustration.

Sometimes, however, the purpose of traffic lights is to keep the flow of traffic slower to improve safety for pedestrians, bicycles, and other drivers. Especially in down towns when it seems like the light cycles are specifically designed to thwart your desire to simply cruise through at the speed limit, that might literally be happening.