The truth is that those are just niche items. Having a need for both a Linux-grade CPU and a real time MCU-like core is not that common. It tends to show up in projects too advanced for most to attempt.
These parts aren’t designed to be your next Raspberry Pi that mostly gets tossed in a drawer.
Engineers actually use these in real products and embedded systems.
The combination of Linux and microcontrollers isn’t new. It’s a very valuable and common structure.
The comments here trying to dismiss it or call it uncommon are bizarre.
Virtually all big computers (mainframes, workstations, rackmount servers, PCs, laptops, tablets, cellphones, and e-readers) use this architecture: the Linux-grade CPU doesn't directly drive things like the USB port, the HDMI signal, the SSD's flash translation layer, or the hard disk head movements. Instead, real-time MCU-like cores do it.
The only difference is that a lot of them are on separate chips.
Probably programming a computer is too advanced for most to attempt, so that doesn't seem like a legitimate criticism.
That's untrue. Almost all the products I worked with in my last company had such architecture - which we leveraged (this was Ag industry). It's very easy to work as they have shared memory to talk to each other.