I don't see how they are "banned". Banning means "forbidden, disallowed, illegal". The older editions do not fall under any of the definitions. They are harder to get, because the author stopped selling them. You can still find them somewhere, and if you already have them you can keep them, they are just less convenient to acquire than they used to be.
You’re trying too hard to defend the indefensible. eBay and Amazon stopped the used book market for these not just the publisher and rights holder.
According to your take no book has ever been banned in the US and people who complained about book banning were clutching pearls.
In the case of Dr. Seuss books, the near-simultaneous decision of the copyright owner to stop publishing them and of the largest online reselling market, eBay, to forbid selling and buying them, makes them, if not literally banned, vastly more inaccessible than many many other books that have been covered under the Banned Books Weeks event, written about in the media, celebrated by liberal readers (in those prior ages where liberal readers thought that right to read was more important than right to forbid) and so on. Your narrow-minded insistence on literalism is just a way of displaying your ignorance and unwillingness to engage with these difficult questions.
I do have a problem if they ban the older editions.