I don’t like pitchers who walk hitters. It puts pressure on your defense. The less walks you have, the better your chances of getting through innings. More walks lead to overworking your bullpen, sometimes just by having to get somebody up, just in case.
There's just not a lot of inventory, and to find a shortstop or a catcher, or a centerfielder, that you think that could stay at those positions... they're very hard to acquire. Sometimes you have to overpay for them, because of that lack of inventory.