I'm afraid I don't see where having a random shop keeper generator would be useful. Unless the seller is a plot device (will give the character information, try to rip off the characters, lie to the police to cause the characters problems or what ever) I simple don't worry about them. If a character wants to buy something and is where it reasonably expected to be sold they can just do it without roleplaying the transaction. If the seller is a plot device, then the attributes of the seller are determined about how they fit into the story and not randomly.
The idea is to roleplay the encounter. Plus, many of us simply do not find it reasonable that every shopkeeper would have every item. Having an inventory generated for a store makes it much more real. Having someone interesting to talk to, even if it's the only time you'll ever meet that character, makes it more fun!
And here's the kicker...
I believe that both you and your players do far more fleshing out of personality, and real character, when they are found in a 'neutral' environment. They aren't expected to be hero's, they aren't expected to be xxxxx (fill in noble attribute). In such circumstances, the characters come out of the boxed shells we force them into by sending them off on heroic adventures, and we actually get to meet them.
Granted, a simple encounter at a weapon-smith's shop isn't the only way to accomplish this, but it's a regular part of most games, and in the end it can be quite rewarding, even create new mini-plots and adventures.... (created by the players!)