Why are people putting pronouns in nicknames?

It started on Twitter and started to seep Into discord and I always wonder why people go like Brilliant Rose (She/Her) or Armed Tiger (He/Him) does it matter if we know your gender
We have a username for reasons we don't go onto sites like discord or Twitter looking for the opposite sex to date well I hope not

There are millions of websites out there like Tinder and Facebook

Also on the topic of pronouns what is the difference between
He/Him, He/It, He/They
occasionally I even see He/Her or She/Him
Those confused me a lot
Why are people putting pronouns in nicknames?
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