Some of those languages (especially python & php) utilise C based modules or packaged external binaries. Both of which have to be available / compatible with AR

Some of those languages (especially python & php) utilise C based modules or packaged external binaries. Both of which have to be available / compatible with ARM. When you run pip or composer on Amd64 they often pull these down and you don't notice, but if you try on arm you discover quickly that some packages don't support ARM. Sometimes there is a slower fallback option, but often there is none.