Varlink exists only to be extremely simple. The Linux ecosystem was using D-Bus for basically everything. But there was some need for IPC in early boot, before

Varlink exists only to be extremely simple. The Linux ecosystem was using D-Bus for basically everything. But there was some need for IPC in early boot, before any D-Bus brokers were started. Varlink was the answer, as a simple direct (vs DBus's broker mediated) IPC.