Because the government wants to steal money from and create systems to control people and licenses to drive vehicles have an ostensible need (safety) which people at large aren't angry enough about to revolt over? Unfortunately for the government, people still hold on to their biological function to have/raise children as a 'right' so they can't go forward with licensing childbearing without significant disapproval in the form of votes and probably violence from the populace. But people have a real hard-on for anything which increases 'safety' so if creating a government identification system which requires people to pay in to be a normal member of society and enables the government to remove your ability to participate in society according to arbitrary rules they create loosely seems to increase 'safety' then the people will be all for it.

Sorry if this is slightly off-tangent, but I'm just plainly deeply cynical about everything the government does at this point, traffic laws being a particularly good example. Does ticketing people for increasing their speed to 100km/h just moments before they actually pass the 100km/h sign on the 4-lane highway actually increase the safety of that highway? Probably not, but it certainly gives the government a good revenue stream and if you try to avoid this abject theft they will destroy your right to participate in society by removing your right to own and operate a vehicle.