When did buskers with amplifiers become acceptable?

It now seems that it's pretty standard practice for buskers to use amplifiers.  Who has decided that this is acceptable?

The volume of these things is always uncormfortably high for people like me with hypersensitive hearing.  Even normal people seem to need to stand back from them, causing a secondary problem of significnatly increasing the space taken up by the activity.

I used to make a point of givinga few quid to a decent busker.  Some of them really used to make places nicer to be - the woman who was always in the tunnel at South Ken station during the late nineties when I was at uni was particular good.  But now, regardless of how skillful they are or how good the music is, they are making the world a worse place.