I believe that when companies do this, it's because there's only a single Thunderbolt controller on-board the host, and they think that giving people two USB-C ports, where either port can do Thunderbolt, but you can't use two Thunderbolt devices (in actual Thunderbolt mode, where you're passing through PCIe lanes) at once, would be too confusing. So they force you to buy a hub or dock — pushing the consumer's blame for this confusing quagmire onto the peripheral manufacturer.
> 8 port USB-C hub
And I believe a major reason for the lack of these, is that, if a dock/hub/etc. that consumes a USB4/Thunderbolt host port, wants to be able to expose a full-speed USB4/Thunderbolt downstream port of its own, then that port isn't going to work for peripherals that are picky about speeds/lanes if you have any other USB devices plugged into the hub. So vendors choose "the ability to plug a single Thunderbolt device in, plus other things" over "the ability to plug a bunch of USB4/3.2 devices in."
> 8 port USB-C hub
And I believe a major reason for the lack of these, is that, if a dock/hub/etc. that consumes a USB4/Thunderbolt host port, wants to be able to expose a full-speed USB4/Thunderbolt downstream port of its own, then that port isn't going to work for peripherals that are picky about speeds/lanes if you have any other USB devices plugged into the hub. So vendors choose "the ability to plug a single Thunderbolt device in, plus other things" over "the ability to plug a bunch of USB4/3.2 devices in."