Disadvantages:
Lack of independence & responsibility: There is nothing like picking up responsibilities at a younger age. This of course is less likely to happen unless you get out of the cocoon and learn things the hard way! Whether it is managing living expenses or your day-to-day chores or balancing study/work and home. You realize the financial pinch and learn why parents always stressed so much on saving money.
No privacy: There could be several exceptions where parents are super cool and your privacy is not hindered. But let's admit it, in most cases, you have to say good-bye to it when you're with your parents. House parties or blasting loud music is never the same with parents.
Timelines & Restrictions: Your nightlife ends at a time that your parents decide. In certain cases your parents decide who you can be friends with. Most of your travel plans will need approvals or need to be faked as study tours. You cannot watch your favorite TV shows either because your parents think that western culture is affecting your life. F-TV is a strict No-No.
Dependency: You will never learn to be self-dependent as long as you have your parents around you. Only when you're on your own you realize how dependent you're on them for the tiniest things. Learning this at a younger age specially in 20s is the most crucial thing.
You don't have privacy or your space
Living with your parents will strip you of your space and privacy and that can be a psychological burden if you have been used to living alone for a long time.No longer will you have the freedom to walk straight out of bed and head to the kitchen in your underwear nor will you be able to go naked from one room to another. While these were just two quirky and humorous examples, you should remember that you can say goodbye to your privacy and the concept of having your own space.
You won't learn the hard lessons of life
This applies especially to guys and girl in their twenties who have never moved out of the house. There are a lot of tough lessons and curve balls that life throws every now and then. And by living with your parents, you could be shielding yourself from some of the hardships life has to offer.