Why are roasts wrapped in foil?

I wrapped a piece of beef brisket in foil and slow roasted it last week.

It was the beefiest tasting beef that I've ever had.

So now I'm wondering, was it beefy because it was a nice piece of brisket from the farmer's market? Or did roasting it in foil make it better?

Would it be recommendable to slow roast belly pork wrapped in foil?