DNI is something of a special case in BT, standard or Alpha Strike.
It is very much an optional rule, by default no 'Mech, Celestial or otherwise, is assumed to have it (and Interface Cockpit has the benefits baked in, i think). This is because if a 'Mech has DNI controls, it can't be controlled conventionally. So, case-by-case.
Don't recall if DNI has effect in AS. If it does, presumably balancing is up to GM.
EDIT
I'd guess its because the DNI (on the Mech) is more of a fluff piece at the point that everything was stat'd, rather than being something that had actual rules.
DNI cockpit has actually no effect on construction rules (except cost), but the implant provides, when used with DNI-equipped cockpit, pretty good bonuses in standard BT.