Why do airlines hate us?

Sometimes I get this nagging feeling that deep down, airlines hate their passengers. I know that they are just inanimate businesses doing everything they can to squeeze a little bit more money out of their customers, but sometimes their methods and regulations are so counter-intuitive and annoying (and unprofitable) that there is nothing left to say, except "are you kidding?"

Our last trip plane trip was booked through Orbitz (or maybe Expedia - those travel sites start to look the same to me). We needed three seats for me, husband, and 2 year-old, plus a baby in the lap, and when I booked it, I picked our seats. For the ease of the entire plane, I wanted all of us together, and preferably not way in the back. This was January. Fast forward to the week of our trip (the end of March), where my husband receive a trip reminder via email, sees that we have no seats assigned, and takes the time to get us three together.

Well of course we show up at the airport and find we won't be seated together. Apparently they do not recognize seats selected through other travel websites. Now I fly this particular airline pretty regularly. It's the only one with non stops between our city and my parents. Every time I can fly a different airline, I do, mainly because of the idiot stuff like this they like to pull. This is the first time the issue of where I bought my tickets from mattered. They even seem ignorant of the fact that one of our party is a two year old and really can't be seated by herself without violating a big list of safety regulations and probably really ticking off the person next to her.

The same thing happens on the way back. We only manage to get one of us next to our toddler with help of cabin crew and very patient fellow passengers. The only explanation or advice we got from the airline (it's US Airways, if you want to note that somewhere) is that 1) we should have picked seats beforehand, and 2) they don't recognize seat selections from other travel websites, only their own. All of this was said with a tone not of regret or trying to be helpful, but "it's your own fault." One agent at the gate made a point of saying "that's why I don't travel with my children." (To be fair, he went out of his way to help rearrange seats on the plane after I turned purple with bottled rage.)

Some of the worst annoyances of flying - baggage fees, overbooking - at least make sense from a profit perspective. I just couldn't figure out what the airline was getting out of not seating passengers who book together next to each other. Forget about the lone child issue. Wouldn't you think that if one person bought 3 tickets, that maybe he wants the seats altogether?

Or, maybe, that is the next extra fee that will be tacked onto ticket prices. If you want tickets together, it will cost extra.

I hope I am wrong.