So what you're saying is that you'd rather wait until the damage is done before re-enforcing the walls that would protect you. By then the horde has entered your 'garden' and destroyed your crop. Windows was a victim of this kind of thinking for years.
Think of it like this. You've got a harddrive in your computer. Your harddrive is by and far the flakiest piece of machinery you'll ever own (I should know, I've had terrible luck with HDDs in my day). If it flakes out, you lose all your information. All your vacation photos. Your spreadsheets. Your doctoral thesis. All washed away in the blink of an eye, and a chik-chik-chiking noise.
A harddrive could die at any given moment. Are you willing to risk your vacation photos? Your thesis? Using a harddrive is a huge risk! The potential for loss too great! It'd be better if we didn't use them at all.
...or you could play it wise, and backup your stuff periodically. Then you get to enjoy the advantages of having a harddrive, while not having to worry about the potentialities. It's the same situation with a walled garden. Do I want Apple barring me from software they don't approve of? Software I myself might find useful? Yeah, I do run a risk of infection by going to strange sites. But, hell, if I play it safe, the chances of me actually getting infected are slim to none. I'm not quite willing to give up a goodly bit of flexibility to protect myself against something that may or may not happen.
Though this argument is really academic now. With Gatekeeper, you get the best of both worlds. You get the protection of the walled garden by default, but it gives you the choice to step beyond it any time you want.
Based on your own argument here, why do so many doctors, hospitals, clinics and even drug stores now promote influenza shots every autumn? Why should they do that when the odds of any single individual catching the flu is relatively low?
Probably because you're far more likely to get the flu than you are Hanta Virus. And you're about as likely to get the Hanta Virus by going to the mall as you are being infected with a mean piece of malware that wipes OSX off your drive and installs Dig Dug for DOS in its place.
The Mac OS, even before moving to the PPC tended to operate twice as fast as the equivalent version of Windows on an approximately equivalent machine. I'm talking back in the 68K processor days. The PPC accelerated that and even after PPC clock speeds stopped going up, they still ran as fast or faster than a Wintel with double the clock. Now, despite the two platforms almost perfect comparability, the Mac still runs Windows faster than the equivalent generic PC by a measurable amount--though it's not as visible to the naked eye as it used to be.
Right. There's a difference, but it's...eh. It's enough to show on benchmarks, but is it enough for someone to officially say "this Mac truly runs Windows better than an equivalent PC"? It's like saying a car that goes 200MPH is vastly superior to a car that goes 190MPH.
There are quite a few advantages a Mac has over a PC. But raw, unbridled speed isn't one of them. The slight advantage on equivalent hardware is outclassed by the beefier hardware you can get in the PC scene.