Serge wrote:
Such words do exist but there are no 'loads' of them.
It's a value judgement. How big is a load?
Serge wrote:
Or because mixing kun- and on-yomi is not something that is seen very often?
I totally agree. It is a fact that most kanji compounds are 音・音 pairs. However for anyone willing to look for them, there are a certain number (some might even consider it a "load") of 訓・音 or 音・訓 pairs.