Why would a stranger want to take a picture with you?

One time I was at a restaurant with my friend. We were 19 at the time and these two 40 year old looking men sat in the table next to us. One of the guys left to go to the bathroom and the other guy was scrolling on his phone. A couple minutes later, the guy chuckles and came over to our table asking us to take a pic with him to prank his friend. Apparently that was his friends phone. It felt strange so we declined.

Has this every happened to y’all? What could’ve been the guys intention?
Why would a stranger want to take a picture with you?
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