Time, energy, money. If your quality of life didn't deteriorate, then you were either contributing a lot to your birth family, such that the decrease in your obligations to your birth family was offset by the increase in obligations to your new family. Or you were lucky and your spouse has tanked all the increased responsibilities for you.
It's very common for sinkies to continue living with their parents until they get married, and it's also very common for them to do less then their fair share of chores as their parents will still continue shouldering outsized responsibility for chores. They can't depend on parents anymore after they get married and have their own home. The problem compounds when the first kid arrives, and the wife takes a hit to her health from the rigors of chilbirth, along with the increased mental and physical strain of caring for the kid.
Then there's all the additional bills to pay, that comes with getting your own place, and providing for the kids.