Of course there are better ways to do it. 

You have to look at it from a different perspective. 
Is it about testing, if you are a robot ?
yes. 
But it is also about, let you do the work of a robot. 
So, while you proof that you are a human, you do some work for somebody !
In this case i would suspect, google. 
You are processing raw data. 
Normally some parts of this "Codes"  are already known, to test your proof !
And some parts are not processed yet. 
So, half of the interaction is, you proving your humanity, 
the other half is you doing digital work with proofed human knowledge. 

(e.g. re-Captcha words: 
one word is known, (if you get it right, you proved something)
the other word is maybe not known in digital form
(so if you get the first word right, you will automatically help to digtize the other word from a physical source) 

So it's not only about the most elegant way to test you.
It's also kind of proved distributed data process.