When it starts taking you longer to find a share than it does for the pool to find a block you perceive your mining to be "wasted" because blocks will be found for which you receive no payment.
I've not been active in the bitcoin community for a long time now, just randomly popped in the thread to see what's up, and I see this is still a topic of conversation. It's important to note (as you did) it is simply perception/variance, and people don't actually lose any income. If you can only find 1 share every 2 blocks, that share will pay enough that the income per block is still the correct average. This was a common point of confusion and misinformation a year ago. I suspect it will persist forever.