Good point about the single parent - I've done the WDW thing alone with kids - I just make sure to have enough snacks to get through the busy lunchtime or go at 11:00am when there are plenty of seats.
I would say though that bringing up the single parent thing - you'd think this would be a WORSE situation for that person - if there are no tables and now you have your food and your kids...what do you do? I have been known to put my young kids at a table right next to the line so that I could wait in line while they waited and had a snack out of our bag right next to me at the table. This, too, wouldn't be 'allowed' anymore. So that single parent would now be left holding the food and the kids and maybe not a table.
And the 'rush to beat someone to the table' thing....no, I would never do this - I wait my turn for a table. So, if I've been waiting the longest - yes, I would take it. But I would never rush ahead of someone who's been waiting longer.