In many instances people feel (more free to be themselves) especially if they can remain anonymous!
A lot of folks on various websites would never dream to say some of the things they post to another person's face. They don't have to be "politically correct" online.
With regard to online dating sites lots of folks will act in accordance to what they think will draw more prospects. People also do this with "offline dating" as well.
Not revealing everything about oneself or fudging didn't just start with the Internet.
Everyone attempts to put their "best foot" forward to impress new people they want to associate with or possibly get hired for a job. They don't want to blow opportunities!
Very few instantly open up their lives, hearts, thoughts, doubts and reveal themselves to people in person let alone online.
To truly get to know someone you have to spend a great deal of time with them in person.
Truth be told everyone has "secrets" that even their own family doesn't know about. It may take years for someone to figure who (they are)for them self!
Essentially we all have "layers" we selectively reveal.
With regard to websites like HubPages there is no real "upside" or good reason to falsely portray yourself.