Technics 1200’s (of which I own two, and personally worked on hundreds (?) over the years), are permanently wired - and in most cases, both would have those cables, and power, routed and dressed to a mixer so as to dissuade theft.
The x1850 (and mixers of that ilk) all have easily detached cabling, connectors, and power.
So has the manufacturing industry followed a trend, or have the manufacturers decided to cut costs and remove accessories/features that they have deemed weren’t needed, and thus created the trend?
As I said, as a career professional AV designer (and professional DJ), I find the lack of the option to rail mount professional equipment - Whether vertically, horizontally, or at some angle in between, to be frustrating and saddening.
It’s certainly a lot easier for you to choose not to rail mount something that could be rail mounted, than it is for me to want to rail mount something that has absolutely no capability for it.