A common mistake made by new riders. My girlfriend had trouble with this during her MSF course. She dropped the bike 4 times before I finally figured out what she was doing (the instructor was clueless). When she came to a stop, she would turn the front wheel instead of keeping the handlebars straight. Probably a learned memory from her bicycle riding days. Once I told her to keep the handlebars straight when she came to a stop, she never dropped the bike again.
Haven't dropped a bike since 1994 but when I did about 20 people saw it. I was trying to bump start it in first gear and sure enough it started and left me behind (lesson learned, second gear is a better bump start gear). One one Super Hero came over to see if I was alright (learned a little about Sociology that day).
Other dump was in early 1983, literally the night before I left for a 22 year USAF career (that is still going in afterlife as as USAF civilian). I was on soft sand in the middle of the night in the middle of nowhere (literally the middle of the Mojave Desert) and I dropped a big street bike in a soft sand wash. First reaction of course was to jump up and see if anyone saw me dump it. two lessons learned here: first off don't ride when there is too much on your mind, second is that soft sand and big street bikes don't mix.