Medicare, the Dark World

I recently helped my dad obtained Medicare coverage at his 65th birthday, and it provided me with an insight of how medicare works. I have to say that I have never before thought of medicare as nightmarish as walking through the dark world. First, I realized that simply getting medicare requires paying a premium, and that's usually in the range of $100 per month. Then I was told that medicare doesn't cover everything(such as prescription drug, dental, and vision care), and when it does, it pays only 80% of the "eligible" cost. Next, I was recommended to get a supplimental plan (also called Medigap) for my dad. Depending on the plan you pick, it could range from $60 to $200 per month just to cover the 20% that medicare doesn't pick up. Now if you add to it the cost for prescription drug plan, dental, and vision care plans, you're looking at ~$500 or more in health care per month for the retirees. I don't know about you, but my math tells me that this is no better than simply going out and get a regular health care plan from BCBS or Kaiser. So what is the point of us paying social security tax every month?