Then you need to read and reread and reread Havoc Pennington's posts on why he wrote d-bus in the first place:

https://news.ycombinator.com/item?id=8648995

https://news.ycombinator.com/item?id=8649459

D-Bus provides a service discovery system that lets you not only send messages to named endpoints, but also monitor whether there's something on the other end of the endpoint, and if necessary, request that it be started before you send the message in a non-racy fashion.

It also provides a common, typed, structured, discoverable, auditable serialization layer which is necessary for doing API-style IPC, and a benefit besides since when you "just use sockets" you have to do all the serialization and deserialization yourself, leading to possibly buggy code.

Oh, and it also does multicast, which no other commonly used Unix IPC can do.

People who say "I don't see the problem that d-bus solves" aren't looking hard enough and/or are ignorant of the issues of how software gets developed in a modern environment. D-bus solves many problems with IPC under Linux, and makes developers' lives a whole lot easier when they have to connect with other applications or services.