Because like any other game that is not 100% influenced by players and their play styles like Altis was you will eventually hit a wall. Almost all games hit a wall in terms of progression. Even if only a few people want to play we WANT to play with other GSN members on a server with our name so we know the server is run right, nothing is stuck behind a paywall and we can all enjoy playing a game we enjoy together. If someone is willing to take the couple hours to put the server up is it a problem? Even if it's taken down later down the line when resources may be needed - if it's the game people want to play, its what they want to play. A bunch of people wanted to play battlefield after the LAN party, so GSN kept the server so we could all play on a good server.
What is the difference here?
The other thing that always severely limited GSN's Minecraft servers in general was they were always locked and whitelisting only. So even when we had all the Altis Kiddies, they were never allowed to play on our minecraft server so it never got the chance for new people to join and KEEP it populated. With the changes that have happened in GSN in terms of our average user base, there is no need for whitelisting because things are so much calmer now. There is no need to restrict the server and it can be freely joined by anyone that wants to play without having to go through red tape to get whitelisted. It would be as simple as jumping in and go.
The difference is we have ten times the amount of members that have interest in battlefield, where as the interest for minecraft is much smaller. In addition, the BF4 server is gone already even with how many people we have that still play it.
Is there a problem taking unused server resources and putting up a game for people to play? No. But who wants to start building in a server that has a very big chance of coming down? I know if it was me, I wouldn't be spending time in a server grinding if there wasn't a plan to keep it up because of the chance of it being removed to make room for other games. And again, as as admin, I wouldn't spend the 3 hours working on a server to get it running if it wasn't going to stay up. Now, if I had oodles of free time on my hands, sure maybe i'd fuck around with it because I'm bored. But time is precious, and it simply doesn't make sense to dump time into a volatile server.
Those are just my initial thoughts.
Edit: I don't mean to rain on your parade, and I know that we have people that would play Minecraft if we had a server. We just been up and down with Minecraft so many times, and there have been games like it that are newer that we support. Just feels like a step backwards into a direction of a game that most of our community doesn't play.