To race all you need to do is know the map and perfect where/when to jump. After a while it'll get boring and repetitive. In Base (Or PvP) the players on the other side have strategy and can change whenever they want. The mercs also add even more strategy and care into the game. If Race could have hitting it would be great but, honestly, how would that work? If a player, on the prototype map you drew, was allowed to hit another, he could easily push and the race wouldn't even be a race, but more so PvP.
When you play Base you can change your strategy anytime because it's Player vs. Player. Race on the other-hand is pretty much Player vs. Map because there is no fair way to allow hitting in the map. Obstacles will bring fun for like a week then when people realize how to maneuver and understand the map it'll get repetitive, like I said above.
Base with no improvements >>>>> Race "revamped"
Base with more improvements/new maps >>>>>>>>>>>>>>>>>>>> Race "revamped"