I think it's a very contrived attempt at appearing spontaneous
"You know, I wasn't planning on making this video, in fact, I was just going about my daily business. But I cannot remain silent, and it's so urgent that I post I've got to do it right here and now"
Sometimes it's just so you don't have to think about your family or roommates listening in? I don't have a car but I usually only make tiktoks when my roommate's gone cus I feel like it'd be awkward lmao