Since I’ve already compared today’s opinion to Marbury and Perry, let’s reinforce that comparison with the following observation.
Why did Chief Justice Roberts address the Commerce Clause and Necessary and Proper Clause arguments at all? He could have just said what he said about the taxing power and then added a footnote saying: “Because I find the individual mandate constitutional as a tax, I need not address the other arguments made for its constitutionality.”
The answer is: because he wanted to make a long-winded speech about these other issues. Not so minimalist, really.