Making the Opportunity Products behave the same way as the Quote/Order/Invoice Products would facilitate better reporting at the Opportunity level.

This is essential in circumstances where the user submits the same quote to multiple customers attached to the same opportunity, for example a supplier to the construction industry who will quote all of the contractors bidding for a project. They can only win one of these quotes, so reporting on them would result in double counting. Hence the need to report on the Opportunity Products, but these will often (or even always) be non standard pricing.