I think that most people see checking a bag as a hassle. You have to wait to get it after you land, there is a greater chance of stuff missing from it (the more people handle it the greater the chance theft), it may get to your destination late (or worse - it can be lost), some more fragile items may get inadvertently broken, security going through your stuff may shift your stuff around to the point where you need to iron additional clothes upon arrival, changing your plans (taking an earlier flight or a bump) becomes more difficult (sometimes impossible), etc. There are also advantages (you travel lighter, no need to fight for overhead space, if you transfer you don't need to log your additional bag around, you can have liquids) but not enough to make up for the disadvantages.

You have covered just about everything that's relevant to the issue.
Some, not all disadvantages of checking your bags would be [removed inappropriate characterization]

Theft by some baggage handlers or TSA employees is also a problem that should not be there.
I don't have to pay any checked bag fees, but sometimes I check my carry on size bag because I want to lug it from gate to gate and take it through security at every connection. On one such trip, I could have had an 800 Euro bump but for the checked bag.

Okay, I see your issue. Which seems to be a mostly american problem. No one in Europe or Asia ever openend my luggage in my absence!! Yes, sometimes you might have to wait 10minutes for the luggage to appear on the carrousel. Boring, but I'm not going to safe the world in those 10 minutes. Most people are not that important. And by bringing all your huge suitcases in teh plane you delay everythign more then just 10 minutes....
W

My personal record is ~75 minutes (1h15min) at OTP. I had landed from AMS at midnight and was looking forward to sleep. Not only was my sleep cut short by an unreasonable amount of time but I also had issues finding an honest taxi (it was after 1 am).

BOS always takes long. CDG is hit or miss. And so on.

When you land from outside the US and have a connecting flight, you have to pick up your bags and re-check them, only to wait at another carrousel at your final destination. Ugh... not fun.

I should mention that I totally disagree with people bringing large luggage items (I've seen some enormous duffel bags!) on board and then fighting for overhead space. Overall though, when you look at advantages VS. disadvantages of checking bags, add some fees on top of that, I think that most people would rather fly with just a carry-on. (I rarely have the opportunity to fly with just a carry-on and I too had to forgo bump opportunities and upgrades because of that.:()

I thought AA had already installed these sliding seats..... Theirs slideright out of the floor!

Seriously, this sliding seat idea is not going to solve anything, and looks like a glorified beach chair. No thanks!

In Bucharest, sometimes you would have issues finding an honest taxi in the middle of the day in the middle of town.

There's no way a POS could sit in one and would have to buy two and would the armrests rise up? No headphone jacks or power outlets? Even a short flight should allow for entertainment. Plus after the fiasco of the AA seats coming loose, this design makes me wonder how bouncy it'll get for the window and aisle pax. Will that rod the seats slide on eventually become warped leaving window & aisle people sitting lopsided? People may scramble for a middle seat for once!