Of course, people can and do jaywalk all the time. I'm told it's different in some places but I am pretty sure that someone actually getting issued a ticket for jaywalking in Boston or NYC would practically be a newsworthy event. In actual life, (most) people do behave sensibly. Pedestrians cross empty streets at will and drivers mostly don't run over people who cross in the middle of traffic.
Whether you like it or not, there are cars in most areas of cities and pedestrians (and cyclists) mostly interact with them without too much carnage, in part because there are rules that most people follow most of the time.
By way of context as to the vigorous enforcement of this law, NYC gave out 300 jaywalking tickets last year. That is not a lot.
In fact that's only about 2x the number of pedestrian deaths in NYC last year.
And this is a city where everyone pedestrian or driver will take every inch they can. Any driver who hesitates is going to find an entire group waiting for a light taking the opportunity to just start crossing.
I'm not saying people should expect physics to not apply to them, but they should be allowed to cross anywhere they want and cars should defer.
Cars used to have to have a person walking on foot in front of them to warn people with a flag.