But it's not like they don't get a large profit from CSGO cases aswell? Not to mention the fact that the game isn't F2P.
They could easily have good development teams working on both. All CS really needs is AC updates, better hitbox/reg, and occasionally the new maps. New cases always bring in a lot of money, not to mention the large amount of selling on the community market that goes on and Valve earn like 15% of every single sale.
The difference is Gabe really loves DotA, and when they created it he got IceFrog on-board to lead the development, whereas with CS, he doesn't really follow the Esports scene as closely, and is probably less involved with the ideas they work on.
CS definitely has enough players to be worth investing development into it though, I don't think thats a logical argument. I just think they need someone in their office who is really enthusiastic about the game to give them a kick up the arse and get them motivated, as it's unlikely Gabe is filling that role atm.
I also wouldn't mind a CS International equivalent, and Valve should stop monopolising the Rules and Map pools of tournaments so that other event organisers can innovate in the areas where Valve has just stagnated (new maps! People forget the maps used to not be decided by the game creator etc. CPL brought us cpl_mill, cpl_fire and cpl_strike, and ESL brought us Tuscan and Mirage, let's give those guys power to set their own rules and map pools)