So what's the deal with weight stations?

I got flashed by a electronic sign in Arkansas a few months ago to pull in with my truck and trailer. Of course I did not and the wife asked why. I said we are not commercial, not paid and not for hire. Wasn't 100% sure it may not of been a safety type inspection but was prepared to say I didn't see the sign as I have no reasonable expectation to be looking at that sign anyways as a private individual.