This is a big assumption. There are many reasons to release something as copyleft – not everyone that releases BSD-like is actively choosing to deprioritize up

This is a big assumption. There are many reasons to release something as copyleft – not everyone that releases BSD-like is actively choosing to deprioritize upstreaming. Rather, they are choosing a license that is less restrictive which has other advantages beyond non-copyleft. Moreover, using copyleft software doesn't mean using forces you to release code. There are specific interactions that trigger the sharing clause in, for example, the GPL, such as distribution, linking, and so on. There remain many, many uses that allow commercialization that do not run afoul of the copyleft nature of the GPL. I am commenting because I have seen this sentiment repeated ad nauseum on here and, maybe that's not what you meant, but I felt the need to clarify. Moreover, if the code is not AGPL, most online uses do not run afoul, because the code product (say executables) are not themselves being distributed. AGPL was formulated to close this loophole, but GPL code is free from this.