There are some who do. Dr. Jack Newman (one of the stars of field I got to meet) is excellent. But a lot of doctors know only what they learned if they/their spouse nursed. The thing is, lactation management takes a lot of time. You sit there and talk to the mom and ask lots of questions. You observe a feed. It takes a lot of time and, in complicated cases, it takes a lot of follow-up. You need to make sure the baby is getting enough if the mom's supply is low and she's working on bringing it back. It can add up to hours of time, and no pediatrician is going to or can devote hours to this. He or she is probably going to say you should keep trying OR is going to just tell you to switch to formula, because that takes no time at all to say.