Dota 2: 7.0 patch that basically changed the whole game, along with huge patches every few months. They added an entire custom games system along with developing and implementing Source 2. It didn't pay off for a while but now Auto Chess has a ton of non-Dota players addicted (even Kripp streamed it) and is by itself in the top 5-10 on Steam (using the in-game player counts vs Steam stats). They have no way to sell loot boxes to those players if they never play a non-auto chess game, as none of the cosmetics work there, besides having been used by the mod itself on the character models.

CS:GO: Entire new game mode added along with the F2P release, patch support and updates for years, bringing the game from fairly dead at launch (the 1.6/Source players hated it) to 500k players right now.

Also, if Valve was as greedy as you say there would be no market, forcing the players to open the lootboxes to get any item no matter what. As it is, you can avoid opening boxes and just target purchase whatever item you want. This goes for Artifact too, where most cards are pennies, and means the cost of actually finishing a deck is well below other games.