Disproportionate number of librarian villagers compared with catographers

It seems that a much higher proportion of white coat villagers are cartographers than librarians. This is simply an observation but I have heard from multiple people's experiences, including my own, that they are finding very few librarians but a high number of cartographers.

I feel this is a bug because cartographers are only really needed once in the game for the explorer maps but librarians have varying enchanted book trades.