Printers don't solve problems by letting/asking people and designers do a job that they don't know how to do, mostly using a color profile not adapted to the printing ! on the contrary they create much more problems, because the printers are the only guys who knows which kind of press they use and on which kind of paper they print, so they are the only able to choose the correct profile matching their press and their paper... but instead they let the customer make a crappy conversion job without knowing which profile to use.
Customers that learn a "little bit how color management and profiles work" is a dangerous thing.
I was not talking about customers, I was talking about printers ! the RGB workflow exists since more than 30 years and it is the only solution to have the printing match the proof.
If the printer let the customers butcher their pictures in CMYK with whatever profile is by default in his Photoshop (or if the printer do the same mistake), the proof will be bullshit in most of the cases. It is a problem known since the offset printing exists, everybody, every customers, every printers in every country always complains that the printing doesn't match the proof, and instead of using the solution that will fix this problem everybody goes on over and over with old habits and old methods that have already proved since years that they are crap and they don't work.
You know the definition of insanity ? according to Albert Einstein, insanity is repeating the same mistakes over and over and expecting different results.
On the contrary, if the printer asks for RGB pictures, makes the proof from the RGB pictures and then does the conversion to CMYK in a controlled way, with the correct profile (correct printing process + correct paper) and with calibrated screens the printing result will be much more predictable.
That being said, the first step of learning a little bit about color management and profiles is simply giving to your customer the correct profile he has to use for the job he wants you to print.
(And if he doesn't use the profile you tell him to use, then you have a good excuse when the printing doesn't match the proof !)