Thunderbolt 3 ports can provide 15w of power. If you fill them up with devices, especially ones that draw power, then your docking station very quickly needs its own power source in order to make them all work. I've already had a docking station refuse to extend my laptop to multiple screens because it needed its own plug.

Anywayz im not arguing that they dont have advantages. Im arfuing that they aren't necessarily better than having individual ports dedicated to specific functions.