That is likely not the case at all. Apple likely (need to double check this) uses some of the pcie lanes for a USB-A hub and HDMI (no free lunch).
HDMI doesn't use PCIe lanes. AFAIK the HDMI in the Mac Mini uses the spare internal DisplayPort connection that would drive the internal screen in a laptop.
The M-series chips clearly have a few spare PCIe lanes - but it takes
4 - plus some plumbing for DisplayPort and power - to implement a Thunderbolt port. That's enough to run a USB-A port or two, an ethernet port
and a SD reader (you can see how the SD reader and Ethernet are connected on a Studio by rummaging around in System Report). Or you could plug just
one of those into a TB port and waste 3 lanes of PCIe bandwidth... or plug in a display and waste 4... or plug in a hub, connect USB 3 devices to it and
still waste 3 out of 4 PCIe lanes of bandwidth.
A future without floppy disks, without analog modems, without wired network cables, without ADB or PS/2 connectors, without optical disk drives
The thing about all of those technologies is that they
were well and truly obsolete when Apple dropped them: the new alternatives were many times faster, had many times the capacity, were a fraction of the physical size
and were cheaper. I mean... my optical drive still comes out of the cupboard a couple of times a year but I surely don't need one built in (they were always the first component to fail anyway...)
What the disciples of the One True Connector still seem to be in denial about is that, even today, the majority of "USB-C" peripherals are still running the same 15-year-old 5Gbps protocols as USB 3, if not 480Mbps USB 2. 4 USB 2 devices plugged into a Thunderbolt hub are
still only sharing 480Mbps of bandwidth with the same USB 2.0 hub latency. DisplayPort over USB-C is still just DisplayPort. HDMI over USB-C is just DisplayPort with a DP-to-HDMI chip in the adapter. Devices that actually use Thunderbolt/USB4 are still priced at a whopping premium - partly because USB 3 speeds are already "good enough" for so many purposes (e.g. all but the fastest external SSDs).
The reason USB-A hasn't died is because, for many people, there is no advantage to it that justifies buying new kit.
My Kanto speakers use Toslink/Optical which is connected to my Calgdigit 3 Dock.
Talking about old tech,
TOSLink - est. 1983!!!
Beautiful example of something that doesn't need to be thrown away because it still does its job... but if USB-A is obsolete (it isn't), that would make TOSLINK archaic (it isn't).
...but I make that 13 years older than USB 1.0
Remember the good old days when Macs had an optical out buried in the 3.5mm jack?
Why is the DAC made with a USB B port instead of USB C ?
Because the typical DAC only needs USB 2 speeds (CD-quality stereo audio is 1.5Mbps, USB 2 is 480Mbps) and there haven't been any huge advances in the state of the art (the frequency of the human ear is still 20kHz less than 'audiophiles' think it is) to change that. USB-C is more expensive to implement, Thunderbolt/USB4 even more so, some people prefer the larger USB B jack for studio/stage work and you can always get a USB-C to USB-B cable if you need it. However, most people recommend connecting DACs directly to the host rather than via a hub.