>>11942027~10 years ago, developers and publishers generally didn't have the option of waiting and releasing DLC for their games, they had to actually finish the game before allowing the public to buy it. Any money they'd make from the game would generally come from direct sales, there was no extra revenue to fall back on from DLC.
Now, they can pretty much withhold content and get away with it, they plan DLC from the get-go that otherwise would have just been part of the retail game years ago before the advent of DLC. They're just taking features and little 'extras' that weren't extra before and, sometimes, charging you for them.
Expansion packs existed, but they were few and far between whereas for more games made today get DLC. You're right, DLC not inherently bad. I agree DLC is great in theory, and not all developers and publishers abuse it, but unfortunately that is what happens most of the time.