Why do apps like Snapchat or Instagram need 15 employees?

I'm a high school student and I really want to learn programming, I want to make iPhone apps (note: I know nothing about programming now). I read that Snapchat has 15 employees, which kind of saddened me. I want to make my own app in the future, but I don't even have 5 friends! So, does that mean it's impossible to make such a great app (like Snapchat or Instagram for example) without a help of other people? Thank you. Any tips are appreciated, like I said I really want to make iPhone apps.

Do some research on those companies. If you had before you asked this question, then you would have known that both of those large apps were developed first by Kevin Systrom (Instagram) and Evan Spiegel (Snapchat). After gaining traction and raising venture capital funding, they found those other employees. It's worth noting that if you had an app that successful, you'd have plenty of people banging on your door to work for you.