This is my pet peeve about USB-C laptop docks. The vast majority of them have a captive cable, usually about 10cm long. It's a failure point, often an inconvenient length, and makes them much harder to pack.
As much as I truly love replaceable cords, I'd be more than happy enough if I could just unscrew the shell of the device, unscrew the power wires from where they attach, and put in any cord. Where I care about waterproofing, some silicone caulk is an extremely cheap (and removable) fix.
Unfortunately practically everything you can buy now is welded plastic halves, or easily-broken clips. So even when you might be able to do this internally, you have a high chance of breaking the shell even if you know what you're doing.
One very practical reason that comes to mind is waterproofing. Kitchen counters get wet, and office desks do not. Anything with a plug is at greater risk of shorting.
That's one of the reasons I love Festool's tools, nearly all of them have detachable power cords. It's a proprietary connector, but it makes it very convenient if you own a few of their tools. Both the power and dust hose have twist lock connectors that stay firmly attached in use.
I’m a big fan of this notion. My hot water dispenser has a magnetic power dongle kinda like macbooks MagSafe, but bulkier [0]. Ideally something like that would be more standardized across appliances the way some of the other three prong power cords are.
Take one look at the mess of incompatible detachable cords that come with LED lighting fixtures from China to see what results.
They could have used bog standard IEC 320-C5 cables, but they didn't. Why? Because they wanted to cheap out on the conductor AWG and IEC 320-C5 is quite specific about the conductor gauges and current capacities.
So, the LED lighting manufacturers produced a bunch of cables that are in almost exactly the same shape and size factor as IEC 320-C5 while being just enough incompatible to not invoke the certifying authorities--all to save a couple pennies in copper.
Unfortunately practically everything you can buy now is welded plastic halves, or easily-broken clips. So even when you might be able to do this internally, you have a high chance of breaking the shell even if you know what you're doing.
[0]: https://youtu.be/E2WrHHRYrV4?t=108
https://www.elecom.co.jp/products/MPA-CCMA10BK.html
Most need double isolation and water-proofing, hence not detachable.
It could probably be done, but it likely needs a different type of connector, akin to M12/M8
It seems to be possible, but it’s likely cheaper to have fixed connectors.
So it is expensive
It is cheaper to just attach the cord
That is the reason
Take one look at the mess of incompatible detachable cords that come with LED lighting fixtures from China to see what results.
They could have used bog standard IEC 320-C5 cables, but they didn't. Why? Because they wanted to cheap out on the conductor AWG and IEC 320-C5 is quite specific about the conductor gauges and current capacities.
So, the LED lighting manufacturers produced a bunch of cables that are in almost exactly the same shape and size factor as IEC 320-C5 while being just enough incompatible to not invoke the certifying authorities--all to save a couple pennies in copper.