by the time they are 21, all young people should be living independently of their parents ?
Many young people live in such age separately from parents. but as for our country young people live in this age together with parents.
Many young people live separately from their parents at such as an, but (at least in our country / a far as our country is concerned) people at this age also live together with their parents.
Personally, I think that young adults should live with their parents because young adults can get a better advice from their parents in case they need it. Parents have more life experience than us.
Not all young people (<em>at the age of 21</em> / <em>at 21 years of age</em> / или просто <em>at 21</em>) are able to afford to rent an apartment or to have/own their own apartment. At this age not all young people have the higher education.
It is only a question of time before governments impose a complete ban on alcohol and smoking !!
I do not really agrees with this statement because it seems to me that the government will hardly forbid them soon! If the government forbids something, that doesn't mean that others won't still do it.
Of course, there's far too much tax money to be made from booze and tabacco.