Guys, why do boyfriends send memes to other girls?

i’ve been with my boyfriend for 7 years and he recently met two girls while he was out with his friends and he followed them on instagram and he started to send memes to one of them. and they both posted a picture of all three of them on instagram. this happened in October to November of last year.
Guys, why do boyfriends send memes to other girls?
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