[bombcar]

Or gives them more lee-way for maneuvering or - makes it a tiny bit harder for spies to figure out what orbit they're going to place the satellite before the launch.

Or because someone asked "how high" and got back "as high as you can go".

[snovv_crash]

It could be something with a large fuel tank that can be adjusted in capacity so that it will be 100% of whatever Falcon can offer for the target orbit.