Page "Wild card (card games)" Paragraph 5

Another issue with wild cards is that they distort the hand frequencies.

In 5-card stud, the stronger hands are less frequent than the weaker hands ; i. e., no pair is most common, followed by one pair, two pair, three of a kind, etc.

When you add wild cards, the stronger hands gain frequency while the weaker hands lose frequency.

For example, if you have a pair and a wild card, you will always choose three of a kind rather than two pair.

This causes three of a kind to be more common than two pair.

But if two pair ranks above three of a kind, the two pair will become more common.