I'm sorry I missed this thread earlier. So much misinformation.
People are mixing sales tax and income tax. Not the same.
ebay is collecting sales tax in certain states not out of choice but because they are required to by law, due to the Marketplace Fairness Act and other legislation. It is inevitable that they will ultimately be collecting sales tax for all states that have a sales tax; it's only a matter of time before additional states pass similar laws to those already on the books.
Sadly, sellers will likely bear the brunt of negative ratings and stars, not realizing that it is
ebay not the individual sellers collecting the tax, and that it's not optional.
Regarding the income tax reporting requirement in the U.S., PayPal did not "choose" the $20,000 threshold for federal income reporting. The two-pronged test of $20,000 in receipts *AND* 200 transactions is mandated by law, and applies to all 3rd-party payment processors (e.g., Google Pay, Samsung Pay, merchant credit card processors, etc.).
Additionally, several states have lower reporting thresholds than the federal thresholds, so depending on your state of residence, you may receive a 1099-K even if your dollar amount received or the number of transactions fall well below the federal amounts. Again, not PayPal's fault.
If you want to blame someone for either of these two tax implementations, blame your state and federal congresscritters.