Strange kind of courtesy?

So I was driving home the other afternoon - or at least I was about to, when I ran into an unexpected show of kindness.

Let me see if I can draw you a picture. I was waiting to pull out of the side entrance to the shopping center where I work. That throws me out on to the main road less than half a block from an intersection with a traffic light. Now the intersection is to my right when I leave, and the right turn lane for that intersection starts just about at the side entrance to the parking lot. I was sitting there at a full stop waiting to make my right turn onto the main road, when a gentleman in the straight through lane took pity on me and stopped to let me in. That was very nice of him since traffic was pretty heavy at that moment.... but there was one small problem. I couldn't take advantage of his gesture because as he sat there stopped, there were people passing him on the right trying to use the right turn lane. So if I had pulled out into traffic, I'd have been slammed by one of those cars. Yet the guy sat there for a little while, perplexed as to why I wasn't taking advantage of his kindness. You would have thought he'd have noticed the other cars as he stared at me - but maybe they were invisible on one side? Anyway, the guy finally gave up on me and took off, and I sat as more cars passed in both the straight through and right turn lanes. Less than a minute later, another guy in the straight through lane stopped to let me in - equally oblivious to the right turn lane traffic. So that left me wondering if there is some new eye disease or something that allows you to see stopped cars but not moving ones?