The "I am not a robot" thing is quite common in websites where you need to sign in, although it's usually done with a picture of some letters/numbers which you then have to type into a box. It's called "captcha" (don't know what it stands for, can't be bothered to Google it). In this case I believe there's some code in the background which can tell that you've manually ticked the box using a mouse (rather than an automated script doing it).
The purpose is to prevent people writing automated scripts which hit the login system thousands of times trying to guess your password, and then using it for nefarious purposes.
So, in summary, it's not childishness, it's protecting your email security. Be thankful it's there.


