, to answer your question on the medical sector: there would be no such sector without patents. Medical research for a single drug can take up to many billions of dollars (or euros), with the end product being one single molecular structure that may or may not work. Research is very, very expensive. It takes years to earn back the R&D expenses.
Without patents in this area, all investments would be void, since everyone would just steal the competitor´s product instead. However, the acceptance of re-patenting of a specific mirror-formula of a product of which the original patent was expired (breath here :-) ), is an example that even in this field, patents are very much imperfect.