Pedro and 2,500 K's

I didn't realize that Pedro got his 2,500th strikeout last night. Pedro becomes the 26th player to reach the 2,500 mark - 14 are already in the HOF and 4 are certain first ballot players when eligible (Pedro, Clemens, Randy Johnson and Greg Maddux). That's 18 out of 26 (69%).

There are 25 players who have reached the 3,000 hit mark - so statistically the two accomplishments are about even as far as degree of difficulty. 20 of the 25 who have 3,000 or more hits are in the HOF and 4 more are considered locks (Ripken, Gwynn, Boggs and Rickey Henderson) while the fifth with 3,000 and not in the HOF is Pete Rose.

HOF voters are clearly more selective with strikeout pitchers than singles hitters. Why is that?