Also, this let us run on machines which aren't necessarily running rsyslog (you could use it on a Windows machine, provided you had tail installed).
imfile just injects messages from the tailed file as if they were read from another source. rsyslog just lists a bunch of sources, then dumps all the messages (based on filter) to a destination of your choosing. If, at the end of your configuration you have something like this:
Plus, if you want to put your logs in PaperTrail without using Ruby, there is this for winston: https://github.com/kenperkins/winston-papertrail