Not everyone can afford to purchase health insurance during open enrollment period. Winter season is full of holidays, short days, and missed work days due to weather. Young working adults very often are not in a position to make anymore sacrifices during such an uneasy time.
Inability to purchase insurance at a more convenient time will perpetually deny coverage to low-risk, healthy young adults, putting more financial pressure on existing subscribers, and leaving young people defenseless against potential medical emergencies. Being denied the ability to purchase insurance is worse than not having any by choice.