You gotta be careful when using "practical" knowledge as a matter of superiority over others. Ofc practical knowledge is important but some people just learn stuff because they love learning. Einstein didn't developed his General Theory of Relativity so one day he could make the GPS. It was not about being useful, its about curiosity, salvation and doing what you love.

As Elon Musk said it cannot always be about solving problems. There needs to be a reason to do so. May it be salvation or survival.