Why is my iPad still on iOS 9

It is possible that you have an older iPad model that cannot be upgraded past iOS 9.3.5.

If you do not know what type of iPad you have, go into the Settings App, under General, About and post your iPad’s model ID number, so we can confirm what iPad you have.

I have a model MC705LL/A

That's an iPad 3, it only supports up to iOS 9.3.5