Your initial assumption is a bit flawed. You can not just draw the conclusion that all friction is the same. It is like saying all birds i know of can fly thus all birds can fly. Which is obviously untrue. Moreover, continuing this similie, you also imply that there is only one kind of flight.
In reality friction is a highly complicated phenomena that includes a lot of the things we don't deem worth thinking about in our day to day life. In fact if you have ever seen the formula:
F_f= \mu F_n
You have seen a physicist saying i have no idea of how it works but seen a simple property. Everything in your question is hidden in the symbol $\mu$ and the formula is approximate. Also by the way the formula is actually $F_n <= \mu F_n$ which is even less useful to answer the question asked.
See, the friction coefficient is highly dependent on not just the material pair, but also the quality of surface finish, surfaces capability to carry the load, how the materials react on the interface, temperature, lubrication and geometry. But it gets better, rolling is way different it has much lower friction so a roller bearing has just the fraction of the friction a conventional sliding contact pair. Even better you can have no solid contact at all. Typically this is achieved by lubrication, but there are even bearings that do this naturally like airbearings or magnetic bearings that don't even have touch anything.
It is not always even about the efficiency increase. Rather about controlling the wear, or some other characteristic. See by having specialized pieces you can change them if damaged, you can spread the load so they last longer, and you can get these cheaper than manufacturing them yourself. The bearing can even have a function in aligning the shaft properly and thereby reduce vibration.