Closures are used as objects quite a lot in R, as the standard structures are all actually immutable (to first order the only common user facing mutable things

Closures are used as objects quite a lot in R, as the standard structures are all actually immutable (to first order the only common user facing mutable things in R are variable bindings / environments, there are reference classes like RC and R6 but they are not considered core language). A lot of R users may not know this as value mutability is simulated through aggressive variable re-binding.