> R is perhaps the closest, because it has data.frame as a 'first class citizen', but most people don't seem to use it, and use e.g. tibbles from dplyr instead.

Everyone in R uses data.frame because tibble (and data.table) inherits from data.frame. This means that "first class" (base R) functions work directly on tibble/data.table. It also makes it trivial to convert between tibble, data.table, and data.frames.