Easier is better some times and most of those systems on that list are simple to run in either stand alones or in RA so why anyone would want to spend time to get them working instead of just playing them I won't ever understand. There must be a dozen NES emulators you could set up just by adding the .exe to LB and then the games and just clicking on the game it will load with no settings, no BIOS files and no command line parameters. I could see using MAME/MESS for a system like CD-I because of your lack of choices but to use it for platforms that have multiple choices that are much easier to implement and run with at minimum the same if not better quality is a no brainer to me. RetroArch is amazing but at the same time I don't use it to emulate every system it can. I don't use it for MAME, Saturn (I use it for A.M.O.K. becuase its the only emulator that it works on) PSP or PS1.
Also most if not all of these posts are biased by the individual users preferences and I see very little empirical evidence of why anyone should switch away from what they already prefer to use including my own post. I just know that the pros of using other emulators over MAME for every system personally outweighs the cons of using it for that purpose. Good luck with whatever you decide to move forward with.