Well, here's a usecase.
uri <- paste0("file://", system.file(file.path("doc", "tm.pdf"), package = "tm"))
(I hope that @jennybryan doesn't ignite the keyboard that this example was composed on.)
library(here) uri <- here("tm.pdf")
So, anytime you have a function signature looking for a full file path for something in your working directory just use the snippet