Biden said he would reinstall the unpopular penalty as a way to ensure healthcare for all. He further stated that "Medicare for all" would be available if people wanted but private health insurance would not be eliminated, saying "If you provide an option for anybody who in fact wants to buy into 'Medicare for all,' they can buy in. They buy in and they can do it. But if they like their employer-based insurance, which a lot of unions broke their neck to get ... they shouldn't have to give it up."
he mandate was made part of the Obamacare roll-out in 2009 when it became clear that Congress would not constitutionally be able to force every American to buy health insurance, so the consequence to being uninsured became an income-based tax levy.
Most that were subject to the penalty in early years were younger, healthy Americans. The penalty was often waived for those that claimed they couldn't afford the increased prices of health plans available in the Obamacare 'Healthcare Marketplace.'
Biden was key in the construction of Obamacare, and has spoken highly of it throughout his 2020 presidential bid, despite the fact that it has decreased in popularity, even to many Democrats.