Never witnessing results of a problem isn’t the same as never having a problem.
I’ve played with several of my scales and balances and effectively, the science is palpable. You CAN induce observable influences in almost all scales and balances - but by and large, for properly tuned loads, the sensitivity is of nearly no consequence. Of interest, yes, even balance beams are sensitive to variations in electromagnetic fields.
Should it be ignored entirely? Nope. Moving a lamp around a room with a few CFL’s or moving a scale/balance around a room, setting your phone beside your scale/balance, turning different lights on and off, even moving big metal masses (like a press) beside your scale/balance, etc all can promote measurable shifts on the device. Is it sufficiently sensitive to become dangerous? Nope. Is it a major issue? Nope. I had little faraday cages to set my scales into in the past, but I don’t bother with it any more. I just confirm my weights and recalibrate if I move anything.