As I mentioned earlier, there are a ton of possible reasons why sometimes it makes sense to take the first pitch. As others have stated, there are also some good reasons to be aggressive on the first pitch. While you should be careful not to use MLB stats, there is no doubt that getting ahead in the count and working the pitcher are both important to the success of a hitter. Sometimes, I have instructed my teams in the past for everyone to take the first pitch the first time up, because we were either facing a pitcher who I thought may have a control issue, or because my team was overanxious and swinging at a lot of bad pitches and either getting behind in the count or not hitting a good pitch they could drive. I don't have any stats to prove it, but I believe that my many players over the years haven't fared well when they swung at the first live pitch they saw that day, and I also hate low pitch count innings for the opposing pitcher. I also am going to sometimes (not always) have my batters take a pitch until they get a strike when we either need a lot of runs late, or when we're ahead in a close game and approaching a time limit.
With that being said, I agree that players can sometimes get too passive with such a strategy, and then have that carry over to situations when they need to be aggressive ... e.g., they are facing a pitcher who is consistently throwing strikes and/or who they ought to be able to drive. That's why I liked the one idea thrown out there to sometimes (not always!) challenge them to not get a first pitch called strike on them.
The best teams are able to utilize different approaches in different situations, and are not totally predictable. A team that always goes after the first pitch is going to see a lot of bad first pitches, and a team that always takes is going to get a lot of good pitches. Players need to learn that they won't always be successful doing just one thing ... but they do need to have a consistently good swing and a good knowledge of their strike zone and their strengths as a hitter so that when they do swing, they are swinging at good pitches that they can be successful with. If they swing at a bad first pitch and hit a weak ground ball or pop up, their at bat is over and they haven't helped their team at all.