I know why this happens.

It happens because someone doesn't understand that search rankings vs. queries have to have a 'smooth' solution, and thinks they can tweak a few weightings here and there to get the results they think are 'correct' for the very specific cases they have in mind, without realising that this has a knock-on effect on the entire scoring space and you get odd singularities and stuff popping up as a result.

The people in question should not be touching anything even distantly related to a computer in any professional context.