Is it that hard for people to remember passwords?
A few months ago an online retailer account of mine was hacked into. Luckily I got an email and shut the account down very quickly but from there I realized that I was using that same email & password combination for a bunch of sites. I ended up on a mass password changing spree, in the middle of my work day, and the guy still managed to get into a few other accounts. All because I was using the same password.
So, yes. It's hard to remember passwords because I use something different for every web site. You should too.