On antique table or floor lamps with two or three clustered sockets, where each socket has its own pull chain (typically a setup seen on stained glass or Tiffany lamps). Was it set up this way in order to have two or three brightnesses (such as turning on just one socket for lower light, and both or all three for brighter)?

Just wondering how these lamps are meant to be used.

I’m guessing so, or otherwise all two or theee sockets would be wired to a single pull chain I would think. 🤔

Might also have been done to make wiring simpler because the switches are integrated into the lamp holders and require no special wiring. Just a semi-guess, however.

I believe that your explanation is more plausible.