They get hurt more than hitters do. In addition, even if a pitcher does well, his cards don't necessarily rise in value. To collectors, pitchers aren't as exciting as hitters. A player who can bash 35 homers is worth more than a pitcher who can post a 3.50 ERA, even though a 3.50 ERA is tougher to accomplish these days. I tend to shy away from pitchers like Ben Sheets, Ryan Anderson, Josh Beckett, Rick Ankiel, C.C. Sabathia, etc.
Hitters are safer bets.
When to Sell Just as important as which cards to buy, it's important to know when to sell the rookies you buy. Generally, it's best to sell when everyone else is buying. Even though Armas hadn't done a thing on the mound to warrant his cards to rise in value, his cards were hot because people started realizing the potential of this card. He's a pitcher and he could underperform, or get injured. So I sold them at the time while they were hot, plus I made some money out of it.