Is it common for people who only wanted you for sex to come back for an emotional connection?

I had a few casual dating experiences and they would have made it clear they were not looking for anything serious. Some of them I never saw again, but I had a couple try to contact me and trying to rebuild a connection after some time. Why does this happen? Is it because they gave up on some person and thought to contact you again because it is convenient or because they are lonely?

Is it common for people who only wanted you for sex to come back for an emotional connection?
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