For my work, I personally have:

• Webcam
• Mic
• Dongle for mouse
• Dongle for headset
• Wired keyboard
• Monitor 2 touchscreen
• Macropad
• Ethernet adapter 1 (connection to work network)
• Ethernet adapter 2 (connection to small switch with no uplinks, for device testing)
• Ethernet adapter 3 (connection to local avoip network)
• External drive
• Microcontroller programmer (universal, let me cut down on a few other adapters I had)
• Serial adapter
• Card reader
• Video capture - analog
• Video capture - digital
• Audio interface for xlr I/o and my good headphones
• NFC reader/writer

Then a couple of loose cables for connecting the random devices, like a tablet for adb purposes, DSLR, etc. Not including the built-in devices on the laptop which show up as USB devices, like the crappy built-in webcam, microsd only card reader in the worlds stupidest spot, etc.

I'd say its easy to hit 15 - thats only the USB devices attached to my work laptop.

but why would you need [thing that is already technically possible and could conceivably be needed]???

Are you an apple dev?

My bukakke VR simulator require between six and six hundred USB devices.

one physical USB-A socket on the machine can read as two USB ports virtually due to that physical socket supporting USB 2.0 and USB 3.0 at the same time, I believe its a backwards compat thing. I think there might also be internal (virtual) USB ports as well but don't quote me on that. On mobos with 8+ physical USB A sockets it can easily get past the 16 limit unless you specifically disable the USB 2.0 port, which then might break older devices relying on that and it becomes a whole headache. this person explains it better than I can

Off the top of my head: Sensors. E.g. in some underfunded university lab.

It's not actually that hard to get up there. Mechanical keyboard, wired mouse, external drives, headset, webcam, other peripherals, etc. And if you are trying to do anything more involved like music production, you end up needing way more (audio interfaces, midi controllers, etc.).

I'm probably past that.

Anyone who produces music with hardware and hasn't spent the extra money to buy a dedicated MIDI interface.

Video. If there is something mindlessly excessive, it's always video. And if you have tree leaves for budget, instead of slightly more expensive hardware controllers or PCIe cards that can combine multiple inputs and outputs, and do it right, you default to cheap usb dongles per device used, and compose them on software level. If you collect inputs from several devices and output these to something like displays on a scene, while also collecting audio from mics, DJ deck, and outputting these too, numbers add up quickly. This clownshow is further expanded by unreliable software, usb power limits, Microslop Windows in most cases - because pros use it or Mac, no penguins. I have no pride in greatly exceeding what some random PCs could predictably do, for fixing random errors here and there when USB and USB hubs hit their practical ceiling is just another level of Dante's hell, for all us time- and harware-restricted tinkerers.

I helped run a Kickstarter where one of our rewards was Mac and PC software on custom USB sticks.

We had a couple hubs set up and cloned the drives 20 at a time.

That’s called a rat king

Okay but you're still stuck with an old x86 version of MacOS,no?