Why do people mistaken my friendly personality as flirting?

Valid question. Even innocently meant things we write are often taken in ways we didn't invite. I think the answer to your question is that many whose eyes we meet desperately hope it's "more." Having come to realize that over my years leaves me with a soft spot for them. For better or worse, I usually add a smile to the mix. Nine times out of ten we go our separate ways, with the warmth of the connection leaving both of us one notch the better because another human being has acknowledged our existence and by their action they've given us their vote. Simple approval puts a spring in our steps that can last the whole day...both his and mine, too. It's a viewpoint worth considering.