Why would my 10year old daughter want to join Instagram?

I do not want her on any social media sites until she is 16. I bought her the iPhone for school only and I found that she has downloaded Instagram, Snapchat, games, and etc. She is turning into her 15year old sister who somehow has 2k Instagram followers. Why do kids need social media? I'm 43 and don't use Facebook or anything.

This thing called "attention seeker".

She's probably an attention seeker and wants to be cool in school.

Coz it's cool and you have no clue what life is about, I would suggest as a parent you get on those social media sites and monitor what your teenage / child are getting up to on there

To post selfies and show how cute she is