Well they may not be useless to real estate agents and crooks, but the painters promote them as valuable for emergency workers. Emergency workers have maps that will show them that it is the 4th house from the corner on the southside, so one doesn't have to look for numbers. Probably the most use place for the numbers would be in rural areas but then they probably don't have a curbs to put the numbers on.
What gets me is how many business have not numbers showing on their buildings. Often in looking for an unfamiliar business address, I pas dozens of building with none indicating a number. Incredibly dumb.