I mainly use BeamNG for its amazing content creation support, and to drive around in/with the things I've created.
The variety of things you can do, and the content creation is actually enjoyable because BeamNG supports you, unlike many companies which would try to shut you down.
I use Beam not as a game, but as yet another canvas for creating things. I enjoy designing maps and car paint jobs, they're a fun little time-waster and they have a little bit more utility than just old fashioned pencil and canvas.
Just the overall realism for me. I love the way the driving, drifting and crashing you do in the game gets pretty damn close to what would happen in real life.
Bought the game because of its crashphysics but now i start it mostly up to race around. But tbh its the whole package of the game. Without the crashphysics the racing wouldnt be so intense. Without mods there wouldnt be still interesting combinations of vehicles and tracks. Without tuning i couldnt finetune the perfect car for a certain track. Without the community there wouldnt be mods and enough input for the devs to improve the game overall.
I see you are a man of culture as well. It's hard to find a server without bus-obsessed 12 year olds, though.
my favorite thing about this game? Unlike other games, that require teamwork, just to have some fun. I can relax and just drive. Unlike other games, that hide advantages behind Pay to Win mechanics (IE SW:BF2). I don't have to hope, for the right battle card or grind for the car i want. Plenty of mods, if i want something special. Unlike other games, that hide end game content behind DLC's (IE Destiny 1 and 2), there is no level. We are all in the end game. I also have Paladins, World of Warships and Warplanes, Watchdogs, Fortnite Battle Royale mode, Paragon and Warframe, This gets played more than all of those combined
I like Beam for two reasons: number one is the amazing crash physics; and Two, the amazing customization. That's what I always look for in a game, customization. It's amazing. Oh, and the ability to brag that you have the game with the most accurate physics EVER to your GTA playing friends.