Other folks have pointed out there are military applications, and I read a while back that these kind of "space planes" have a unique advantage: with their wings they can dip into the atmosphere and very quickly change their trajectory without using a lot of fuel. From a military perspective, I'm guessing this makes them harder to shoot down. The military is still flying space planes [0] so this makes sense to me.

[0] https://www.livescience.com/spaceplane-lands-after-908-days-...