Space planes carry along heavy-as-fuck wings, control surfaces and a lot of other bullshit that's only useful inside the atmosphere, and which massively increase fuel consumption for every single maneuver while your space plane is actually where you want it to do stuff - in space. And the only benefit is that the atmosphere helps lift and fuel your vehicle to about 10% of orbital velocity. The other 90% it will have to accelerate just like any other rocket.

The SpaceX approach is much better: Land and reuse all parts of your rocket, but don't carry them with you further than where they're useful. Rockets leave the atmosphere where wings would work within a few minutes anyway.