Programming: blank password not recognized in UNIX?

So I'm using OS X (a UNIX based OS) and try to do things in terminal. I rarely use password on my personal computer, so I just skipped it in OS X installation. Apparently, OS X recognized my password as empty/no character. So if any program required and admin permission, it will ask for a password and I just keep it blank and continue. 

Apparently, when trying to do a sudo command on UNIX, it does the same thing: it asks password. However, if I keep it blank, Im not recognized as admin: I failed to write files to specific folders such as /usr/local/... . 

The solution is to change my password so its not blank. I works fine after that. 

Anyone else experience the same problem? Is my theory is true?