Traffic lights - I think this is down to "progress" when traffic lights first came into use, the amount of traffic was much less, most of it being commercial rather than private cars. As traffic numbers increased then individuals then felt that their private space was being infringed upon thus making them want to keep moving. Another reason may be that cars now "feel" safer so more risks are taken. I do not think there is a timescale for this to have changed, its simply the fact that with the increase in traffic its more noticeable
Trousers - I blame that one on television advertising and the advent of the designer label syndrome of the early 60's that the short trousers started to disappear. It was roughly at the same time that simple plimsolls went out of fashion and the trainer started appearing.
Queues - your theory on the design of the bus and the bus-stop seems pretty good, although the main reason must be a simple lack of good manners and also a lack of common sense.
As for the driving receiving a thank-you, this I believe stems from when people started using taxis rather than public transport, and as you would not think of tipping a bus driver then a thank-you is the next best option.
Right back and finish of the daily crossword now.