I'll address each of these as a bike commuter. The underlying things to remember are that a) while cyclists are expected to obey the same traffic laws as operators of other vehicles, sometimes there are safety reasons to violate them, and b) the light weight and low speed of bicycles means that while cyclists are vulnerable to harm from motorists, motorists are not vulnerable to harm from cyclists.

Red lights: cyclists should stop for all red lights, but should not necessarily be expected to wait for the light to turn green before proceeding[0]. This is partly because of sensor-activated lights that may never register the presence of a bicycle, and partly because it can be safer by separating the cyclist from traffic waiting at the red. You should also pay attention to how many motorists run red lights (usually for 1-2 seconds after they turn) and stop signs.

Crosswalks: cyclists should slow down for crosswalks. Remember, though, that "full speed" on a bicycle is nothing like full speed in a car. You should pay attention to how many motorists also speed through crosswalks.

Not signalling turning: cyclists should signal all turns unless they are in a situation where they need both hands on the handlebars. As a motorist, you may not be in a position to judge when that is.

Not using bike lane: in most jurisdictions, cyclists are encouraged but not required to use the bike lane. There are good reasons in some cases for not using the bike lane. A bike lane that is next to on-street parking may place cyclists in the door zone[1], making it more dangerous than taking the lane. Bike lanes may also accumulate road debris and be unsafe to ride in.

Hope this helps explain some of why cyclists ride the way they do.

[0]: https://en.wikipedia.org/wiki/Idaho_stop [1]: https://en.wikipedia.org/wiki/Door_zone