State Speed Limit

I have a question about the New York state speed limit. I understand the rational for its existence, that's not the issue. What I question is the state's decision to include "State Speed Limit" on its road signs.

The state speed limit in New York is 55 MPH. Of course, 55 MPH is not appropriate everywhere. Sharp curves, city streets, interstate highways, each needs a limit tailored to the individual road conditions. At the very least, the state speed limit is a starting point. In the programming world we call this a constant, perhaps SPEED_LIMIT. With computers we can just substitute SPEED_LIMIT in place of the value 55. If we decide to change the limit we need only change one line of our program.

This analogy quickly breaks down in the real world, but that's my point. The state can't just say SPEED_LIMIT on their signs because not everyone knows the value of SPEED_LIMIT. They can't update SPEED_LIMIT without updating every sign. They can't very well let 55 MPH be the default speed limit and just say when the limit is different. (Picture a sign that says "End Speed Limit" and the wreckage a few hundred feet down the road.) Every sign that says "State Speed Limit" must also say "55." This strikes me as a waste of resources, however minimal. (Though there are likely thousands of these signs in the state.)

Does anyone know the reasoning of adding "State Speed Limit" to the road signs? Every state has a state speed limit, but why say so on the sign itself?