When live music was permitted, not all kingdom halls had people who were talented enough or ambitious enough to play. I remember guests at the hall I attended making comments about the live music. I think it is a shame that a person who is willing and able to play (competently) isn't allowed to because of corporate policy.
I don't know how many people in my congregation or any of the other congregations that meet in my hall could play the songs nowadays. I just remember seeing these starry sheets of party piano music--I'm talking 20s or 30s--because you could count on people knowing how to play piano, more or less. So you figure, you have these starry folks who grew up being taught piano as part of their social upbringing, and you could count on that sort of thing to be done at the hall. Nowadays, I can only think of one chap (now df'ed) who could really play who was around my age. People aren't taught piano as part of social upbringing.
So rather than nowadays hope for the one guy in a thousand who could really play the piano at the songtime, you just have a blanket policy. It takes the soul out of singing, most assuredly, but I reckon that They aren't too concerned about it.