All passions count

I like to say that anything can become a great career with enough creativity. Tell him to decide how much he is going to put in to making his drumming a source of income. I had a friend who was a percussionist. He studied music and became a professor. At some points in his life, they had to supplement their income with a family band that played at gigs. They made it work. Your friend could teach drumming, or make a you tube channel or join a band, you never know.

That being said, if your friend is not willing to be creative and work really hard to get his name out there, a back up might be a good idea. Studying something in college does not mean you will do that the rest of your life. And you can study more than one thing in college. We tend to make this decision a lot harder than it really is. There are so many possibilities.