I disagree. There are plenty of skill games, that are extremely difficult to write a bot for. Even something like a rock-paper-scissors bot is a daunting challenge. Deviate from the nash equilibrium (a random throw), and risk being exploited. But if you play randomly, and you have only downside (assuming a rake).
Why do you consider rock-paper-scissors a skill game?
It is mainly luck based IMO, though if it is played face to face, you may be able to read your opponent's gesture and predict his movement.
When I think about skill games, I immediately think of games like chess and backgammon, which people have created extremely powerful bots...