If you don’t have a dongle, the dongle is basically just hidden inside (a chip on the main board or an extension card). Being able to add dongles is a very easy way to quickly add things like wifi. Otherwise you’d have to open the PC and mount a card and the number of slots inside is also limited. So yeah, builtin is good, but also no, dongles can be better. It’s just a different option.

I guess you could use the same argument to say you’re buying less when you buy your laptop. It’s just arbitrary data I/O through USB with the software level interpreting it. They don’t have to ship a DAC or wifi radio or… whatever you call the component that’s part of a GPU that converts to HDMI, instead they offload that to the dongle or peripheral. In effect your device is just slowly being whittled down to a processor to USB bridge.