In theory, there is no need but you have to keep in mind that there are some instances where alot more drag in necessary. The 80 and 130# class is usually braid with a mono topshot. The braid allows you to LOAD the spool.
The braids have a much thinner diameter which translates into more line on the spool. However, it is not a necessity and many people do use straight mono of 80, 60,50, and even 30#.