Did you ever hear the tragedy of Half-Life the Third? I thought not. It's not a story Valve would tell you. It's a PC gaming legend. Half-Life was a first person shooter, so popular and so profitable it could use the engine to influence the modders to create new games... It had such a fanbase that it could even keep other titles they cared about from dying. The profitability was a pathway to many abilities some consider to be unnatural. It became so powerful... the only thing it was afraid of was delivering a mediocre final chapter, which eventually, of course, it didn't. Unfortunately, it taught its creator Valve everything about making money from selling hats, then its creator killed it in development. It's ironic it could save others from being vaporware, but not itself.
-KKlear, Reddit