Chains should be required in some, but not all, conditions BUT only in countries where people know how to drive in snow (like Canada). Americans do not know how to drive in snow (at least those Americans from California). Why do I think this? Because my car was totaled by Americans on the 1st day of the season in Tahoe (N*).
It was a great sunny day and N* was just opening. 1st day skiing in the states. Decided to head up for some relaxing laps. The road was wet with a bit of slush but mostly clear. I was driving around 45-50 nice and in control. Americans thought it would be a good idea to go 65+. This idea failed when traffic began to slow to a stop. Cars were flying into ditches to the right of me, unable to stop, while others decided to use my car to stop. End result - 3 month old car totaled.
Chains are a good requirement in Tahoe just for the purpose of keeping speeds down!