The laws of physics means that the longer the path for your network packet, the higher the latency.

One way latency on the Internet across fiber is about 4μs to 5μs per kilometer in my experience.

For example, SF to Paris is ~40ms one way (it used to be 60ms 15y ago, latency and jitter have really improved).

Double those values for the round trip allowing you to interject in a conversation.

Add wifi, which has terrible latency with a lot of jitter (1ms to 400ms jitter is not uncommon). Wi-Fi 7 should reduce the jitter and latency in theory. We shall see improvements in the coming decade. Cellphone 5G did improve latency for me, so I don't doubt WiFi will eventually deliver.

In other words you need to be within 3Mm (3000km) away to get a chance at a 30ms roundtrip. And that's assuming peer to peer without wifi nor slow devices.

For a conference call, everybody connects to a central server acting as the relay. So now the latency budget is halved already.