Why would someone choose to fly VFR on top?

Subject line says it all. In light of the fact that VFR on top subjects
you to both VFR and IFR constraints, why would anyone ever choose to fly
VFR on top? I can only think of two possible reasons:

1. There happens to be clear air at a +500 foot altitude and not at the
corresponding even-thousand altitude (though how would know that without
popping up 500 feet to have a look is still a mystery).

2. You can get a more direct routing because of the less restrictive
separation requirements.

Have I missed a possible reason?

rg