I have gotten the update for Fallout New Vegas, and this bug is still happening.

Every time I play a game of Caravan, the NPC will not bet any caps. I can buy and sell goods from them, so I have seen that they have plenty of caps. They never bet any money.

Is this is a bug, or do I need to reach some sort of milestone before NPCs will bet on a game of Caravan?

I hear some people have re-installed after the first update and NPC bidding is now working for them. I haven't tried it myself.

I had this issue.

I linked it to the fact that my character never got the caravan primer from the guy in Goodsprings. He preemptively excused himself from the gene pool. Next time around I did learn from him, and then everything was fine.

Of course we also had the first patch in between as well, so it's not exactly a controlled experiment.