We don't know if GPL works in court. It roughly seems like whatever you write in a license is an effective deterrent though. So your repository could take an existing permissive license like MIT, and add a clause like I mentioned. Set a procedure for your terms for others to use your open-source project commercially. An example of this is the Big Time Public License.[2]
[1] https://wonko.com/post/jsmin-isnt-welcome-on-google-code/
[2] https://bigtimelicense.com/versions/2.0.2#big-business
Because that isn't open source, and is arguably not enforceable anyway.
How do you define "make $1M"? There are mega corporations with billions in revenue that somehow have a negative tax bill each year, so clearly taxable income isn't a reliable indicator.
Conversely a non profit organisation may have several million in donations/income but spend all of it on their charitable causes.
So clearly net revenue isn't a reliable indicator either.
If you don't want to release software under a licence without monetary terms, then don't. No one is forcing you to do that.
>> Why don't our overworked, underpaid open-source developers license their software
Of course they absolutely can license their software any way they like. That is their prerogative. Personally I write software for a living and it's all licensed with a commercial license.
By definition then I am not an Open Source Programmer. (I work on the odd Open Source project, but that's not the same thing.)
So any programmer can license things anyway they like. If their license is Open Source compatible then they're free to call themselves an Open Source programmer.
Your suggestion is equivalent to asking why an amateur golfer can receive prize money in a professional tournament. They very much can though, but then they're no longer an amateur.
If lacking precedent is your main concern, there are no software licenses that are likely to fill your criterion.