I have been poking around at USB modems and it appears that, at least in the US, Verizon, Sprint and AT&T are only offering a single USB based device. They each have 2-4 mobile hotspots each.
Is this the global trend?.
yes they are dinosaurs and thus unusable
There are plenty of things a dinosaur can be used for. The problem is that they are hard to come by 
One possible solution (for modems, not dinosaurs) is to get an m.2 modem (made for laptops or embedded) and a USB enclosure with a SIM slot. But this will probably be much more expensive and bulky than the traditional USB stick modems.
I am understanding that there are now some embedded solutions (SoM) that are prequalified by the vendor and can be just plugged into a device. Not sure why this is different than a PCi card (which I think is the m.2modem, not sure). Skywire, Dragonfly
The issue is I am not aware of too many devices other than the GL.iNet MIFI and PC-Engines APU series with the support for these. where does one get a USB enclosure for a m2 device and sim slot (Which I think basically becomes a "mobile hotspot" that is replacing the USB sticks).
Unfortunately we do not have any type of USB device listing which makes knowing what devices of any type work frustrating.
What countries are you from?