The issue in Idaho is a bit different than in most states. Idaho has a nearly uniform 6% sales tax rate. (The
exceptions are added local sales taxes in Driggs, Hailey, Ketchum, Lava Hot Springs, McCall, Riggins, Sandpoint, Stanley, Sun Valley, Nez Perce County, and the Boise and Pocatello auditorium districts.)
In comparison, Washington has many dozen different sales tax rates (each county, and some cities, differ), and each is riddled with various exemptions.
So there aren't just 50, but thousands, of different local sales tax rates in the U.S. These have to be cleaned up before interstate sales taxation will be practical. That's the goal of the interstate compact, which Idaho refused to accept in the news story posted above.
If Idaho refuses to collect interstate sales taxes, then it could become a big shipping center for mail order/internet businesses. Both the advantages (sets a practical limit on excessively high tax rates) and disadvantages (limits tax revenue) are apparent.