No web-surfing with administrative account: why?

I get the idea that there's bad stuff you could download & install, but not exactly how being logged in to Windows with a non-administrative account helps.

If I download something which requires administrative permission to do its harm, why can't I prevent it by just not giving permission (or not downloading it in the first place)? If there's something I could download that doesn't require that permission, then how does using an account that couldn't give it help? Are we talking about something I wouldn't know was happening, or something I would see giving me pop-ups to confirm that I want to download and run/install it? This advice sounds futile for the former and unnecessary for the latter.

Is this advice really just meant for those weird users who would just randomly download stuff willy-nilly, and those who are responsible for the computers those users abuse... but irrelevant to a single home user like me who has no other users on the same machine and would be the sole user for both accounts anyway (and knows not to download & install random crap)?

via International Skeptics Forum http://ift.tt/2aXMbLR