The first is that I think you are good-looking and want to pursue you, but I'm afraid I won't find you the first time I meet you, so I want to further develop with you and enhance our feelings.
The second is to do marketing to attract customers, which is the most common situation; He handed out leaflets. When he saw that you received the flyer, he thought that you were an intended user, so he asked WeChat to further communicate and promote sales.
I hope the above answer can dispel your doubts, thank you!