"I'm curious. too. If I've missed BP's previous explanation, for some reason not to manufacture these, I'm sorry.
When I first saw the 9.5 packs a few years ago, I thought ALL the string companies would have them in no time. I have been very surprised, they didn't become popular. To those who haven't tried them, the .5 DOES make a difference.
Ever tried to explain the difference of one thousandth of an inch [9-10] to a non-guitar player ? ? Play 10's a few hours one night, and then the next night, play a set of 9's. Oh yeah, you'll know the difference. I think the 9.5 sets are a happy medium between. I'd love for Ball make to make a 9.5 set. If not sold in sets, offer the 9.5's and 11.5's etc. as singles, to make up your own gauge preference.
My 2 cents worth." M.S.