Okay, here's a few things about Space Engineers. 1. It's not free, you have to buy the game, and if the server you want to play on is using the purchased DLCs, you have to buy the DLCs 2. Servers cost money to run every month and someone has to pay it. It doesn't matter if you're renting a server or running one from home, there is a cost. Now for some home servers all the cost is just the extra electricity and the normal maintenance of the server, but for others the server owner has to pay a much higher price to their ISP for the necessary bandwidth for the server to run properly. Who pays for it, well the server owner/operator of course, and sometimes the couple of friends that got together with the owner to get the server started.
All of the 'free' online games out there aren't really free, there is a cost involved in them somewhere. Maybe you're paying for it just by the ads you have to click through at times. Maybe it's paid for by all the costumes, skins, armor, and weapons that are available to purchase by cash/credit. Maybe it's paid for by any donations the people running the game servers receive. However the costs for the games are paid for, they are being paid for, at least until the day they aren't being paid anymore, then the game goes away.
So anyways, here's Dual Universe they have decided to offset the costs of running the game, the players will pay a subscription of some sort. You pay the subscription, you can play, you don't pay the subscription, you don't get to play, simple as that. All of those other 'Free-to-play' MMOs out there have some gimmick to get money, and so long as their particular gimmick keeps giving them enough money to pay the bills every month they won't go to a subscription, but when the gimmick fails to get them enough money, that's when you see a previously free-to-play MMO suddenly talking about requiring a subscription in the future, or just completely shutting down.
Anyways, I've said my part, agree with it, don't agree with it, I really don't care. Just remember, there is always some type of cost, sometimes you get to see what the cost is, sometimes you don't.