Pretty standard really. You don't want contributions to the codebase come under questionable copyright concerns, or the original creator to revoke the code 4 years later causing huge headaches potentially.
You typically have to sign these types of CLA's whenever you need to contribute to any serious project. I've had to do it for Google and Microsoft recently, and I've done it for various other open source projects as well.
Still that shouldn't concern users/gamedevs as they don't contribute to the engine code typically. Only if they want to upstream changes back into the engine publicly they would need to sign it ofcourse
I'm a game dev, so my perspective on this can be biased, but my honest opinion is if games are too expensive for you to buy, go pirate them. That's exactly the situation places like Argentina are in now. Let us westerners subsidize the cost of development until your country gets back on track and you are able to buy more than just staple goods (40% of Argentina is considered living in poverty or worse).
This goes for people in poverty anywhere in the world tbh even in the West. Piracy doesn't really move the needle much (but do try to support indie devs if you can)