How many times have you gone to do something on the interwebs and you can't remember the password to do said task? And the thought of going through the password recovery makes you abandon the task all together?
The first barrier to any project, personal or professional, is usually having the password readily available. Can't go anywhere without it and if you don't have it at your finger tips, it's too easy of an excuse to not do the task at-hand or take longer to deliver something to your boss, to your client, to your peeps waiting on you.
Put them in one place, together, and make sure they are secure. The easier the access, the more you will rock at whatever you are doing.
You probably have hundreds of them. I have 503, not including client passwords. That's a lot of passwords.