I think maybe he didn't want anyone to know he was good at it, is all I can think of. Although how many times would that game up in trying to get a game?

But I guess there could be some rich dude that got to where he thought he was good at it, then it would come in handy to play stupid and pretend it was going to be the 1st time you ever played it.
Sounds interesting...though the first sentence is a little off, now that we know Dennis played it extensively.
Kind of like darts I guess where you have to go out on a specific number, which makes it harder. Sounds interesting though. I can see a lot of strategy involved. I'm sure it's a lot more invovled then just swinging at balls. Like bumping a ball towards a pocket but needing to leave the balls in position for the next guy to where he can't get to the one you moved there and hoping you have the ability to carom into it, rather then them. Sounds like a way to make your quarters last a lot longer on a bar table

I'll have to give it a try on my next free pool night just to see how difficult it is to reach 101. I would be very interested in seeing it played by 2 good players just to get a idea of the strategy.
Although popular enough that its rules remain listed in authoritative rule books alongside just a handful of other games,[3] apart from a small sanctioned tournament held in 1914, cowboy pool is strictly an amateur game.[1]
Rules
Cowboy pool uses only four balls, the cue ball and three numbered balls, the 1, 3, and 5. The balls have a set opening placement: The 1 ball is placed on the head spot; the 3 ball on the foot spot; and the 5 ball on the center spot. As in the game of snooker, pocketed balls are immediately respotted to their starting position. Beginning with cue ball in-hand from the kitchen —the area behind a pool table's head string —the incoming player must contact the 3 ball first. If the player fails to do so, the opponent may either force the player to repeat the break shot, or elect to break him or herself.[1][3]
For the first 90 points of the 101 needed to win the game, points are scored in three ways: 1 point for caroming the cue ball into any two object balls; 2 points for caroming into all three object balls; and a player scores the face value of any ball pocketed, i.e., if the 3 ball is pocketed, the player scores 3 points. Thus, the maximum score possible on any single shot is 11 points, achieved by caroming off and pocketing all three balls. The failure to score in one of the delineated manners on any shot ends the player's inning at the table. All fouls in Cowboy pool result in the player losing all points scored during the inning (not just those on the fouled stroke), and the opposing player comes to the table with cue ball in position except in the case of a scratch, which results in ball-in-hand from the kitchen.[1][3]
The 90th point in cowboy pool must be reached exactly and the failure to do so is a foul resulting in a loss of turn. For example, this means that a player with 89 points, who then scores 2 points rather than exactly 1, has committed a foul. Once the 90 point benchmark is reached, all points up to the penultimate 100 must be made by caroms. The pocketing of balls during this phase of the game garners no points. The final point necessary to reach 101 and the win must be made by a losing hazard – an intentional scratch made by caroming the cue ball off one of the three object balls.[1][3]