There are ways to pass the coordinates in a VoIP 911 call. Unfortunately, these standards are designed by astronaut architects and are rather cumbersome. For instance, one uses MIME multipart bodies inside a SIP message. Which few systems handle properly (because it's such a bad idea and has no practical use cases).

Instead of being engineers and saying "ok, well just throw in a header X-911Location" or something simple, they gotta make shit complicated. It's ridiculous.

They also use this IETF designed address format. Which is rather ... comprehensive. All sorts of designation for streets and branches and so on. Except... none of the 911 systems actually use that. So they design this protocol with no care to how actual systems work. Or how actual street addresses in the US work. They basically made up their own idea of how address topographies could work.

But I'm guessing some of the larger companies doing VoIP probably have it sorted (like when you do a VoIP call on T-Mobile and there's no GSM just WiFi).