The reason why is that those devices create arcs, and AFCI breakers are completely unable to handle them. Some regions require AFCI breakers, so a significant portion of household appliances will occasionally trip the breaker.
The worst part is that it isn't particularly consistent, so your fridge could last for years without tripping it, but as brushes wear the arcs they regularly create increase the chances of a trip, until one day you find that all your food is ruined, because the AFCI breaker tripped at an inopportune time.
Fortunately, my fridge trips the AFCI very reliably, so I was able to detect it before losing any food. All I had to do to fix it was make a few passes with the hot wire through a ferrite bead, right before it connects to the AFCI breaker. It completely blocks the arc-created RF that the AFCI is detecting, disabling the functionality of the AFCI, all without any code violations, because while the AFCI is required, the ferrite bead isn't prohibited.