Why IC driving 232 can not drive multipoint systems & we need to use rs-485 standards.

If balanced s/g is difference bet. 232 & 485 then how this balanced system is so superior to signal system like 232 carrying signals wrt. ground.

even in case of 485 system we need to make ground common or at least it is better to do so.
Then what r the advantages of 485 over 232
I am not talking about it carries data over longer distance & it is multipoint but want to know why 232 can not be designed in this way?