It was not sysv to systemD, and it was forced (by making udev not work without it).
Other then nvidia, wayland is still missing some protocols (example: what virtual desktop you want your window to be on). But those protocols are (still) being worked on. And you will always be able to run x11 programs on wayland.
The advantages of wayland are a more direct path to hardware, and trowing away lots of code.