So question is why doesn't the US make it a mandate to have daytime lights? It saves lives!!
Daytime lights are available. People have the option of turning headlights on for themselves if they wish (I do...but I also wear a helmet in a State where none is mandatory).
If ONE person sues an automotive company alledging real loss because of a lack of daytime running lights they will instantaneously appear on all cars without Gubbamit intervention. It's just a quick software change in the ECU for most cars. Many cars in the US already have them, but I think it's mostly to keep from having to produce a second ECU setting for Canada only cars.