It gets people used to clicking URLs in emails. This is a bad habit.
if people really cared, they'd follow The Rules. How many other conveniences do we drop? I rarely click links in e-mail, but my non-technical eternally trusting-of-strangers friends will always be tricked into doing stupid stuff. If it's not links in e-mail, it's pop-up-windows, or salesmen with extended warranty.
Ignorant people aren't fungible, they're people. The more idiot proof you make things, the more idiots you save - it isn't binary.
>How many other conveniences do we drop?
We evaluate them on a case by case basis, because we're thoughtful people.