>>34788567Weather system + larger pool of Pokemon.
Due to more Pokemon being introduced, the odds of you hatching a good Pokemon from an egg is growing slimmer and slimmer with each generation. And with the weather system making level 35, high IV Pokemon even easier to obtain, those level 20 Pokemon you hatch just aren't looking all that appealing anymore.
I suppose you could hatch for the EXP, Candy, and Stardust. However, level 40s don't need the EXP, and you have no control over what Candy you get or how much of it.
Spending 3 days (or $1.50) worth of hankebucks just to hatch three eggs faster just doesn't sound worth it anymore.