I don't think so ... I think it's just been the trend for years and years.
I tried to find out, if I had to have it for ALL or most or what ... didn't get a direct answer. And each time though, was reminded that I'd better make sure I followed the rules .... then tell me the rules and answer my questions! :)
It was kind of a last minute decision to enter last year, in two shows ... and so I was panicking and dashing to get them ready. Thankfully, only the one show required the rod pockets! So that saved some work for me. Have kept my pockets and safety pins, ready and waiting for another time.