This is the baffling part. I live in a country that periodically grades the taste of regional water supplies, in addition to testing for solids and the usual. And I live in a part of that country consistently known for really great-tasting tap water.
It's baffling that they'd sell water in a can. Please don't tell me it's bottled in Atlanta, where they bottle the worst-tasting coca-cola in the world, or it'll be extra-baffling.
Maybe the appeal is the "cool factor". Here's 2 examples I could think of. At work, you want to stand out from the "water bottle" people. At parties/bars maybe you don't want to drink alcohol, but still want something in your hand while you're mingling.
Insulation and conduction are opposites. Vacuum (empty space) and stagnant air are great insulators, that's how double walled bottles insulate.
Aluminum conducts heat quickly for the same reason it conducts electricity well. It has a relatively low heat capacity too so it doesn't take much energy to heat or cool it so it will more quickly heat or cool its contents.
Toss that alu can in the freezer to cool it quickly, then put it in an insulated colster to keep it cold.