Another consideration (apart from the 64MB ROM / 8MB RAM configuration OpenWRT targets, up from 32MB / 4MB in 2010) is that the original—and still very popular—platform for OpenWRT is Linux on big-endian MIPS, which does not exactly have ubiquitous compiler support outside of the C world. (Rust treats it as Tier 2, on par with Windows on ARM and Solaris on x86-64, which isn’t bad as these things go.) So—Go is about as realistic as Java, OCaml I don’t think runs on MIPS, neither does MLton, and IIRC the GNU Ada implementation was in a much worse state then. There’s also the part where the devs are by necessity C hackers, what with sorting out the manufacturers’ kernel patches and all.