People enrolled in private plans with better benefits don't have to enroll. A specific example is retired military who can enroll in a medicare wrap around that has better drug benefits.
My Dad's a WWII vet and the VA ships him every drug he needs. My Mom pays BC/BS $50/month and gets all her meds.
They're happy with the new plan. They're 86/83 and both take heart meds and God knows what else.