The point of an MVP is to get the product in the hands of users as soon as possible to test viability and garner feedback before going down a rabbit trail that may not be successful. It isn't necessarily to start making money from customers before the product is ready—although being willing to pay for something in alpha is probably a good viability indicator its not the only one.
Many games aren't treated like products but more like hobby or art projects. This isn't a bad thing but it does mean an MVP isn't really necessary or helpful. Many games do things that achieve the same results of an MVP:
1. Screenshot Saturdays. This puts the idea in front of people even if the thing is buggy, broken or just unplayable.
2. Festivals. User testing during festivals was incredibly valuable and helped us determine what attracted players to the booth, what they enjoyed about the game, what was fun, what wasn't, etc. Here the game doesn't need to be finished.
3. Awards. Similar to festivals, an award can indicate that you're on the right track. The inverse isn't necessarily true. Winning an award does not equate to market viability.
4. General social media, spreading the word and press. If someone is willing to talk or write about your game that's a good sign.
5. Steam's Greenlight: Will people vote for this?
6. Steam's Early Access: Will people buy this before its finished?
7. Kickstarter. A very time consuming and potentially expensive endeavor that might work for MVP-like launches. Will people contribute money to the possibility of this game existing?
The point of all of these is to get out there with the game as soon as possible, even if its not ready, to test out the idea. Some require higher levels of investment than others and make sense at different points in the project.
Experience: we launched our first game earlier this year with success and followed these where they made sense.
EDIT: Formatting