I heard its like a obligation to have real estate or its difficult to marry over there, i can imagine that many people can simply not afford real estate in bigger cities.
It certainly applies to e.g. Shanghai - no house/apartment = no parental consent.
However due to the Hukou issue - more or less every Chinese citizen has a house or apartment. So it's more of a matching issue - our daughters apartment (presently registered with her parents) is worth 6 million - how much is the to be husbands apartment worth? In the middle class upwards it is common for the husbands parents bringing in the $ needed for a down-payment for the future home. Which is 30% for the first property - so at average around 1,5-2 million Rmb in the outskirts of a first tier city - down to 300,000-500,000 in 4th or 3rd tier cities.
The average income for a young couple (25-28 years old) - both working in a 1st tier city is around 18-25,000Rmb/month. So if the parents of one of the two to be married - doesn't have a 2nd apartment, prospects towards marriage get tight.