I heard (secondhand info and all that) that there's some taxi startup somewhere that is using all Teslas, but instead of approaching Tesla about installing superchargers for their own use[1], they decided to just use the existing public superchargers, tying them up and creating long delays for anyone else who wants to use them. So it seems that this new rule is meant to combat that type of behavior.

[1] Apparently companies can approach Tesla about installing their own private superchargers, though I don't know the details.