Not only this, but Japanese "kanji fonts weren't supported," with katakana characters ... Snake obviously didn't stay so quiet forever, however, with him getting an actual voice in Metal Gear Solid, ...

Kanji fonts weren’t supported, and you could only show one katakana character at a time. Solid Snake, the protagonist of my debut title Metal Gear (1987), was born as a silent ‘tough guy ...

Metal Gear's grim and competent special ops protagonist Solid Snake was only grim and quiet thanks to strict tech limitations restricting what his creator, Hideo Kojima, could do with him.