There are two major reasons to file your past due returns as soon as possible

If a taxpayer is due a refund because of withholding or estimated taxes paid, even if they were not legally required to file -- you must file within 3 years of the return due date to receive the refund. (If you owe back taxes - the amount of your refund will be applied)

The same rule applies if you have a legal rights to claim tax credits, such as EIC (Earned Income Credit)

Note: Taxpayers who are self-employed won't get credit towards Social Security retirement or disability benefits.