[xur17]

> If you re-use the same password for all sites, it takes just one sketchy site being compromised for all of your other sites to become compromised.

And speaking as someone that operates a website accepting passwords, this happens more than you'd think. There are hackers that actively try leaked lists of username / passwords against websites using botnets. If your password is leaked by one website, people will attempt to reuse it on other websites.