From another thread.
Back in 1998, when all the SOES bandits and other questionable practices and firms were all around, and people were shooting at one another and "day trading" was a new thing (LOL, day trading has been going on for 200 years)....the regulators were concerned, and were closing down shops right and left. There was talk on Capitol hill about classifying exchange member firms trader's as customers, which would have left a couple of thousand families without a way to make a living. We, and other professional firms, lobbied hard to keep our exchange status for our traders.
The regulators agreed to do so, but they needed a way to distinguish between retail and pro, so they came up witha S7 license...we were happy to comply so that our traders could continue to have all the benefits available to exchange members.
That's pretty much it.
Don