The BSD folks may not be interested in systemd itself, we are still interested in running various bits and pieces of software on top of the platform. When software starts requiring systemd just to run we have no chance what so ever at porting that software.
The same is true for a lot of Linuxisms. I have spent an awful lot of time getting software that states on the tin it is written for POSIX to run on BSD because its source code uses all kinds of Linuxisms.
The same holds true for people assuming that /bin/sh is bash, which may be true on certain Linux distributions but isn't so most other systems. I've started noticing the same issues with other things as well, such as the symlink from /bin to /usr/bin, /sbin to /usr/bin ... whereby software believes all software lives in /usr/bin when in reality that isn't the case for the BSD's.