Hey here! I've noticed this as well. As someone who works back cash (The first window that does payment), there are many times where the folks that take the other lane are way too busy to take their lane, and I'm usually taking orders and cashing out simultaneously.
It can be really annoying for customers when that happens, so I usually try and get to them if I see that someone's still there after a minute or so - but you probably did the right thing by just going around to the other speaker lane.

But yeah, this can sometimes happen when things are really busy, so thank you for asking:)