Not necessarily true - I have driven across the Rockies on I-70 in December with no snow or ice issues. Of course, you should be prepared just in case, but if you keep an eye on forecasts and conditions and adjust as appropriate, there won't necessarily be a problem. Thousands of motorists make that trip on a daily basis. The cotrip.org website is an invaluable resource.

You should be able to buy a set of cable chains for about 30 bucks or so - I've seen them in Walmarts in SoCal.