There are hardly any commemorative stamps in the stamp mixture I just bought - what's going on?

A recent independent sample (not done by us) of stamps received in the mail reported that only around 5% of the stamps used were commemoratives. The overwhelming majority of stamps seen in this sample were coil stamps of various types (almost all self-adhesive).

It's hard to get any large number of US commemorative stamps in bulk stamp mixtures nowadays, and that's why - hardly anyone is using them for their mail.