I think a lot of it is general ignorance about stuttering. Most non-stutterers don’t seem to be aware that stuttering is a genuine speech impairment and not just something that pops up every now and again because someone is nervous or jumbles their words or pronunciation. I’m a moderate-severe stutterer and I stutter 100% of the time in all situations. The number of times well-meaning customers, coworkers, and other people have told me to “relax” or “slow down” is infuriating, even more so when they tell me “It’s ok; I stutter sometimes when I’m nervous too”. Like, I know you mean well, but you clearly have no idea what a stuttering disorder is.