Taking warhammer as a example it's very fun to build and paint your models you can even give them names and lore backgrounds, then you take them to the battlefield as in the tabletop and face them against other armies and you get to see your hard work in action.
Many people don't even play tabletop they just love to paint the models.
You can also go to your local games workshop store and play with others there if you don't have friends who play.