why? Because it feels like your always working to pay off the landlord or the bank just so you can have somewhere to sleep. Even if you own it outright, property and taxes are 10k/y, now your paying $1k/m just to have a place to sleep before you can even spend money and work for the things that you want. The worst of it, is as prices go up there should be a huge push to build more to balance the market, but than you have all these huge artificial barriers to entry to build preventing that from happening.
So it makes sense to try to live with parents, make enough money to buy your house outright so at least than you have a chance to get out from indentured servitude.
To be honest most of us are just hoping the real estate market collapses, or these barriers to entry are overcome so that prices can drop because we are not willing to pay these prices which amount to servitude. Our refusal for this type of "life" is what causes a decreased in birth rates and growth in general in the economy.