Lots of people do this to connect loosely related sentences because to them the "..." reads like a little pause. I guess it feels more comfortable, less formal, and let's them get the words out without worrying about structure too much.

I believe it is due to an unwillingness to make a concrete statement. A full stop is strong and is equivalent to speech in a flat and confident tone. The ellipsis seems to stand in for short disclaimer phrases like "by the way", "in my opinion", "in case you were wondering", etc.

Two otherwise very smart family members of mine both used to do this. It takes sitting down and explaining that email isn't a voicemail. We're not "hearing" the pause when we read, we're just confused and it makes the person writing seem dumber than they actually are.