Respectfully, briar doesn't have a higher combustion temperature, that I am aware of. I haven't done any tests myself. But, regardless, I think the reason that briar caught on was more for its aromatic qualities. The smell of slightly warmed briar complements the tobacco very well. Whereas oak or cherry would stand out as being so different that it would be distracting. As it is, I don't think many pipesmokers even notice the aromas of the briar as it is talked about so little on here. But, when smoked in meerschaum or a clay, the tobacco just doesn't have the pipe-y smell, as it lacks the essential aromas given off by the briar.