Vaccines are traditionally not very profitable. Companies don't have an incentive to ramp up production ASAP because they know as soon as everybody is vaccinate

Vaccines are traditionally not very profitable. Companies don't have an incentive to ramp up production ASAP because they know as soon as everybody is vaccinated demand will tank. There's plenty more profitable things to spend their time and resources on. However, for everyone besides the drug companies it's advantageous to manufacture doses as quickly as possible. It's the same reason DPA is used in wars. It would be vastly more profitable to produce scarce luxury items but not in the best interest of society. The interests of drug companies and society are not completely aligned here and DPA would force them to apply all their resources to the problem, rather than maximum profitability.