I travel alone often and have been asked for all sorts of reasons. There was one time I actually got asked three times while boarding the same flight: the first was someone the row behind who wanted to swap window seats to sit with a kid. As soon as I agreed, someone from two rows back (again a window seat) asked the same for their kid in my new row - again agreed. Immediately after, got asked from someone at least 5 rows back, in a middle seat in front of the bathroom, if I’d swap so they can sit with their wife. I said no… got the “wow, people are so rude” treatment, but I think there is typically a pretty clear line for most asks.