The top flight has been without a backer since May 2013.
Speaking at a Scottish Football Association convention, Hearn said: "If you worked for me you'd be sacked. You have so much good in Scottish football, so many positive things, but you don't sell yourself.
"You don't do enough for yourselves. I'm seeing too much self pity."
The SPFL, which covers all four senior divisions, was established just before the 2013-14 season but has yet to attract a title sponsor.
"You've been in the shadow of the English Premier League and you've almost given up to be honest," said Hearn, the chairman of World Snooker and the Professional Darts Corporation and former owner of English League One club Leyton Orient.
"That's a bit brutal and it is a generalisation, but if you don't believe in yourself, how on earth can anyone else believe in you?"
Hearn also insists the ban on alcohol in football grounds should be lifted for the good of the Scottish game.
"It's archaic in today's world for a customer not to be able to buy an alcoholic beverage at a function or a sporting event," he continued.
Lifting the alcohol ban, introduced after trouble at the 1980 Scottish Cup final between Celtic and Rangers, was one of a number of suggestions from Hearn to help improve the customer experience in Scottish football.
"What you have to do is make sure fans behave themselves," he said.
"That's a security issue for you. If you can't keep your establishment secure, there should be no booze, but you shouldn't have a blanket ban on alcohol throughout Scottish football."
Football finance expert Joe McLean also spoke at the convention and said the idea of Scottish football switching to a summer programme should be discussed again.
"There are obvious challenges and obvious difficulties," said said McLean, of Grant Thornton LLP.
"But other countries, Scandinavian countries, for example, and Russia, have a different programme.
"It doesn't stop these countries fielding teams who feature in European tournaments like the Europa League and the Champions League."

The agency said Movette had used "deceptive methods" to bill clients for the use of Google My Business - a free service provided by the US search firm.
Movette had been in business for two-and-a-half years before being wound up in the High Court.
It had received more than £500,000 in fees before the intervention.
Google My Business is a service that encourages companies to share information and images about themselves to help the tech firm display relevant listings in its Search and Maps tools.
Movette had charged its victims between £199 to £249 a year to manage their entries.
The Insolvency Service said the firm had:
The agency said its probe had followed "a significant volume" of customer complaints.
Several clients had also posted their concerns online.
"This company contacted me telling me my Google page was about to expire and following a conversation claimed I had bought their services," wrote one on the Who Called Me site.
"Now they hound me every day demanding money and threatening to send in bailiffs. They always ring on withheld number but the number to call back on is a premium number. Clearly it's a scam."
Another posted on business reviews website Trustpilot: "Complete liars, rude arrogant... they claim the verbal contracts are legally binding and cannot be cancelled. Do not believe them."
The Insolvency Service noted that Movette had operated a "very similar business" to another company - Online Platform Management Consultants Ltd - which had shut in April 2015 after operating from the same Manchester address.
Sports promoter Barry Hearn says it is "disgraceful" the Scottish Professional Football League cannot find a sponsor.
[NEXT_CONCEPT]
A Manchester-based company that pretended it was linked to Google has been closed following an investigation by the UK's Insolvency Service.