I'm fairly strict, that's all it is.
In the past I was told I was a weak referee who didn't utilise his cards. In all my assessments since I've been able to return to refereeing I have been commended as utilising the cards correctly at the appropriate times and consistently across the 90 minutes. In fact, my only negative in that area is that I missed a caution in one match so...
I don't see it as a high card count tbh, it works out as an average of 4 cautions per game, which isn't much IMO. My average last season was 3.8 (or 1.9 home cautions and 1.9 away cautions). The model of consistency I guess.