What is the function of a rear cross member on a 1998 subaru legacy 2.5 gt ?

I own this vehicle and the engine and transmission is in pretty good shape. It has a little under 165,000 miles on it and i would like to keep it considering I live in the northeast with these crazy snowstorms. This car is great in that is a AWD. Dont want to get rid of it but this is a little problem for me at the moment. Would really like an honest opinion as I was almost duped into selling it to someone who diagnosed it with a wrong diagnosis ( shameful ) just to resell for alot more money as body is still in great condition also.