When I worked for a German mfr (K-M) decades ago, we were required to use ferrules on all connections. Here in the US, that practice was basically unheard of at the time and we got nothing but complaints about them. As I saw it, the saddle clamps used on most devices, such as relays and pilot devices, were designed to apply spring-like pressure to the terminals and keep the wire(s) under control. But with the ferrules, the saddle clamp was not able to "smash" down on them in the same way, leaving them vulnerable to vibration.
I did a huge control system project for a dam on the Columbia River in the late 70s. The Army Corps of Engineers wanted ring tongue terminals on everything, but you can't do that with IEC devices that are finger safe, so I had to convince the COE that the ferrules in the saddle clamps was just as good. They had me stand in front of them with a relay and a wire coming off of a terminal with a ferrule while they added weights to the other end of the wire until the ferrule pulled out (picture in your mind, the background scene in Monty Python and the Holy Grail where they are experimenting with sparrows holding coconuts...). I managed to convince them that it was just as good. But a year after installation, there were so many loose connections that we had to send wiremen out there for 4 weeks to remove every ferrule at our expense and replace them with locking fork tongues. Dams are continuously vibrating, I guess that was too much for the ferrule system.
" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden