I don't know. As someone who has LPed, as someone who has a journalism degree and worked in journalism (poorly), and day dreams of releasing a game like some day dream of that "eventual novel" this issue is one of gray blurs. Even if I thought that was a good idea to get some revenue from LPers into the hands of Devs (besides the LPers having had bought the game, usually), the concept of X% on all LPs is too broad of a stroke for a complicated issue.

At the core of it is LPs are simply a giant blob of different shit that overlap with other things.

• At what point do you consider an LP an LP or a very in-depth walk through/guide?
• At what length does a very long form series quit being critique/review for those who don't mind spoilers into a LP?
• If it is a series by one of those LPers who are essentially vloggers with video games in the background, the audience isn't there for the game. If that discourages a sale (beyond a bad impression a poorly done review could do) then your game probably has some big flaws. A blanket x% doesn't seem fair there.
• How much of the game being shown would count as an LP? A guide channel that shows how to beat all the bosses and puzzles isn't ALL of the video game, but it covers all the non-filler. If the devs of the Dark Souls decided to go after LPs and felt the characters/lore were as crucial as the gameplay wouldn't they then be fair to go after VaatiVidya?

Then there is the issue that the video game commentary industry, for most people, sucks in terms of money coming in. Next to nothing, heh, if they go overboard I wouldn't be surprised if a good chunk are in the negative if they bought a decent mic if they only have income based on advertisements What happens with the inevitable protest where LPers decide to quit using adverts and go to Patreon? Do you then go after that money? Or a Twitch streamer who decides to tell their viewers "Hey, this is our vlog segment. If you want 100% of your tip to come to me instead of only 90% now's the time ;)".