Power
The best part of being an advice columnist is that you have power over your audience.
Of course, if your only readers are your boyfriend, your mother, and your best friend's next door neighbor, that's pretty low on the power scale.
The power comes from page views.
If you have a blog that reaches thousands upon thousands of people per month, you have the power to get advertisers and publishers interested in your column.
The more interest, the greater the opportunity.
"Dear Abby" and "Ann Landers" were syndicated in a great deal of papers, as well as in quite a few magazines. Their large readership gave them power, thus allowing each sister a prosperous career.