Disclaimer: we still have pragmatic reason to follow the evidence suggested by our best scientific theories. I'm just poking fun at scientists in the spirit of Hume. There's no guarantee that the future will resemble the past, and even our best scientific theories are amenable to future evidence.
They aren't universally true because they are just names for things that are universal like quantity. when you have one item you can make any name for the word one but however it is defined it will be one and and if that where not true it would not be simply our concept of reality it would be our reality or our perception of reality which amounts to the same thing. If I find one day that I see four lights but there actually are five then either reality has changed or I have to wonder if I am mad. Or some cardasian is trying to drive me mad.