It's mostly about future-proofing. If I had renovated my house 20 years ago, the "best" copper cable I would have installed was cat5e, which will never get much beyond 2.5G. But if I had installed SMF instead (which was available at the time), it would be compatible with terabit networking hardware that is available today, and the petabit networking hardware that is likely to be available 20 years from now.

When the lifetime of cables in the walls is typically more than 40 years, it makes sense to avoid limited technologies like copper or multi-mode fiber.