Why is it whenever I date a lonely guy, he begins following other girls?

[FictionalCharacter]

I have read girls post similar questions regarding of why guys begin checking out other girls once they’re in a relationship.

For example, (in my case)

I come across a guy who has very little friends online (like 5 close friends). With different gender groups. Till I come along (girl), we begin chatting and develop feelings for each other and then date.

We discuss our future together and put each other first. Then I (girl) begin unfollowing people online to show and focus only on my partner (guy). To put our relationship first.

BUT
What does guy (boyfriend) do?

THE EXACT OPPOSITE

He begins following/adding MORE girls online.

As a girlfriend, I’m cutting people out of my life to put my partner first.

But the guy/boyfriend is adding more options and opportunities? WHY?

Why do guys do this?

Do not say I’m ‘generalizing’. Whenever there are similar or more posts online from girls asking about this.

So can someone explain this guy behavior?

[Xoxocutekitty]

He probably doesn't value you enough.

Guys (like women) are also susceptible to dating up, often using the newfound confidence from one relationship to catch and attract others (sadly) often more physically attractive.

Since he was single for so long, his self esteem probably spirals from unlovable to drama king which creates a weird shell of 'never fufilled' and always ready for the next chase.

[ChiTown33]

This doesn't add up. He's got no friends but all of a sudden all these girls are popping up.
If he's got no friends and these women supposedly wouldn't give him the time of day. Then why are you insecure about it? Have you said you don't like it? And if so what was his response?