It sounds more likely to me that a single driver spaced out and forgot to leave the passing lane than all the others making a switch of lanes impossible. I mean, obviously it can happen too, but whenever I am in such a situation, the slow driver in the passing lane is just not taking the opportunities to switch. If they want to, they are to use their indicators and I am sure another person would let them in soon enough.
It sounds more likely to me that a single driver spaced out and forgot to leave the passing lane than all the others making a switch of lanes impossible. I mean, obviously it can happen too, but whenever I am in such a situation, the slow driver in the passing lane is just not taking the opportunities to switch. If they want to, they are to use their indicators and I am sure another person would let them in soon enough.