In the real world, outside of your conspiracy bullshit fantasy world, they damn near always include all actual fixes in the free patch that accompanies all their expansions. Whether or not you consider a given DLC worth buying is another question, but they're almost always new content/gameplay that you can still play the base game without.
Besides, they're not in any way obliged to add any content, no matter how miniscule and pointless, for free. They sell a game, you buy the game, done. So long as the game contains everything they say it contains you are not entitled to the tiniest bit of extra content.
No, they don't. Utopia, Apocalypse, brave New world, all held changes that the community had been asking for en-masse for ages that were ONLY AVAILABLE to the paid versions. They had slight and minor changes to give you a taste, but even then if you didn't have the paid version you were missing out on the most important factors of the base mechanics that were being addressed in that content update.
Are they obliged to add any content? No, but this is something that game developers have done for years and something Paradox charges for, fixing the base game to a playable and enjoyable state costs us $10-20 piecemeal bit by bit until the game is worth over $200's invested fully in. Remember this is the SAME company that upped the prices 20-40% on an 8 year old title. They're not doing these changes with benefiting the community in any way, and even EA does these kinds of mechanics updates and changes to the base game for free.