Client isolation

Complete isolation on a wired network typically requires one switch port and cable per device. Ethernet frames over the wire aren't encrypted the way 802.11 packets are. Enterprise-grade switches manage port access and authorization with 802.1X or the like.

Between hardware limitations in the switches and the general pain to manage, it's hard for me to imagine it being popular.

On the other hand, I've been keeping each brand of IoT device on its own SSID and VLAN for years now, each with their own DNS and firewall rules.