So you are saying they should do it for the “exposure”.
The core issue is that consulting scales at O(n) where n is your personal time investment. It's not like offering a service where you spend all your time working on the service and get to experience exponential growth.
Basically, if you choose to commit to free software / OSS, you can't expect to get directly paid for it. Now, I know that that's not always ideal and ends up in tragedy-of-the-commons situations where the OSS devs don't get paid enough, but that's the reality of the situation to me.
Restrictive licenses don't solve the problem, because these same cloud behemoths can just pull an open distro on you.
Free in software is not about getting paid. Money is not the problem. You can expect getting paid as much as you want, you just have to let other people access code, change and distribute it as they wish.
Thinking it is "free as in free beer" is shallow. I don't need any of those crap android apps even if they are free, I want to have ability to see those apps code so I can see if they are sending my private data somewhere, and I have to have ability to remove that code. I can even pay license fee if I find some app useful, if price is to high I find alternative or just don't use it.
Free software, in the sense you described, also means you cannot monetize it by applying a restrictive license. Full stop.
The other side is that you probably will have hard time chasing people to pay you, so in essence you won't be able to get much out of it, but that is just side effect.