It's the same as with Linux, GIMP, LibreOffice or OnlyOffice. Some people are so used to their routines that they expect everything to work the same and get easily pissed when not.
A Karen is a (mostly female) person who demands special treatment for no specific reason, who permanently feels mistreated and set back compared to others and someone who always wants to talk to the highest available employee in expectation this person would take her side and take inappropriate measures against the one that "did her wrong"