Why do people say this?

Cause you're lovely 🎶🎵🎶

I know what you mean tho cause when i was a teen we went to these people's anniversary party and the lady thanked us for coming and i thought "why? We didn't even bring anything we are just here eating your food.."

But sometimes that's all that matters is just being there and people appreciate having you around.

They are only trying to be friendly! Would you rather they ignore you?

I wil admit though I do not like "hey!". It is a peremptory word of warning, command or rebuke.

Maybe because they're happy to see you. Maybe they do actually like your company/presence. Maybe they like talking to you or think you're good looking. Maybe they admire you for your traits or the things you do. Maybe they like your sense of style or your general attitude.

I say that when I like the looks
Or I know that person is genuine so it's refreshing to see such people

Maybe they like you and seeing you makes them happy

It's polite and casual & makes them feel better about themselves

so you would rather people weren't glad to you see you? 🤔

It's usually customary terminology at least in the west.

Well they could say,
Oh its just you again.

It’s just a figure of speech, not meant to be dwelled upon.