Well it would be nice if google could check the url it was visiting and if there is any sqli in it to not send the request (though this could potentially slow their crawling...)
http://en.wikipedia.org/wiki/Medireview#Blocked_emails
Even if you look for somewhat complete SQL strings, if I want to host http://try-sql-in-your-browser.io/?sql=select+foo+from+bar, I'd want Google to index it.
http://try-sql-in-your-browser.io/?evil=true
It works well for IPv4.
I just can't justify why do you expect Google to spend resources on not running bogus HTTP GET request when anybody can run those? What is different about being hacked by Google bot and being hacked by an unsuspected user who clicks on a bogus link that was put on the same page where Google found that link to your server? Just doesn't makes sense.
Not only that, but it seems to me that it'd be a more efficient use of resources to spend the time hardening your own site rather than lobbying Google to implement something that only mitigates one potential attack vector. Even then, it just seems stupid because I'm sure there are valid GET query strings that might have select, insert, update, delete, or some permutation thereof in them.
It seems to me that it's just a punt on poor programming habits...