One of the emerging themes in traffic planning, and urban design seems to be the near-universal rule that "Happy cars do not make for happy people"(or particularly healthy ones), yet much of our street design is based around getting cars from place to place at as high a speed as possible. Part of this has traditionally involved putting up signs and marking to make it clear where everyone belongs and at what speed and in what order. However, as Tom Vanderbilt, author of "Traffic" discusses things like "Children at Play" signs and similar markings don't work.
Why is this? In part, excessive and largely irrelevant information just provides an additional distraction, and often gets ignored and partially because overly strict distinctions rob drivers of the ability and motivation to courteously interact with other road users, or each other.
In the particular case of crosswalks, drivers are basically being told that they can ignore pedestrians except at certain places on the road, which in turn usually gets them in the habit of ignoring pedestrians entirely. This isn't a lack of courtesy, it's just that when drivers are not in the habit of looking for people on foot, they might miss them even when they are waiting in a crosswalk.
As a result, it becomes inconvenient and dangerous to walk around downtown, which in turn makes it less pleasant to shop (and shoppers more likely to "just not bother" visiting shops that they have to double back and cross a busy street to get to).
Several "new school" traffic engineers around the world have taken this problem head-on not by adding more crosswalks and signage, but by getting rid of the signs and giving every road user more-or-less equal access rights. The operator of the bigger, faster vehicle is responsible for slower operators, so cars yeild to bikes yeild to pedestrians and everyone watches out for children. Real-world trials of these "shared" or "living" street designs that force motorists, cyclists and pedestrians to interact as human beings have shown that the are both safer and more efficient.
Traffic flow, in many cases, is actually improved (think about it, while your car CAN go 35 mph on a downtown street, you actually spend a lot of it going 0 mph. A steady 5-15 mph is actually much faster and somewhat less aggravating) and increased pedestrian safety makes it easier and more pleasant to wander around, get lunch, shop and spend money downtown, which in turn leads to a better local business climate, better tax income for the municipality and therefore a lower residential tax burden.
There's some argument (and not altogether an invalid one) for banning cars from urban centers altogether, and routing them around downtowns instead of straight through them, but this comes with its own trade-offs in mobility and economic issues. Better to get people in cars to slow down and pay attention than to try to keep them out.
From the business perspective, people don't come to towns where it's pleasant to drive (there is no such place, "pleasant to drive" usually means "middle of nowhere with nice scenery", not "town." Cars are good at getting between places, they usually become a burden once you get there), they come to places where it's pleasant to walk, shop and hang out. If they know they can walk around worry-free, they're ore likely to get out of their car and spend their money.