Update: The long-standing quesiton about whether or not Amazon will be happy collecting taxes on behalf of 3rd party sellers is officially over. On January 1st, Amazon started collecting in 4 more states (HI, IL, MI, and WI). Last October they added 9 (AZ, CA, CO, ME, MD, MA, NV, ND, TX, UT) Georgia and Alaska were added as of April 1st. Mississippi , Tennessee, and Louisiana were added in Q4 of 2020.
That brings the total to 44 states (including DC) that Amazon collects and remits taxes for 3rd party sellers (plus there are 4 states that don't charge sales tax). That leaves only Florida, Kansas, and Missouri. The bulk of the other Marketplaces like Walmart and eBay have also complied with most of the rules, but not as fast as Amazon. For Amazon, the logic is easy.
- They have a physical nexus in all 50 states already (so they pay taxes on items they sell direct)
- They already have an enterprise level merchant collection system that's been running for year
- Walmart, EBay and other compet