Is it because most big console games of the time were made by Japanese studios who only had access to like z-tier Canadian anime dub actors or the first three gaijins that walked past their offices?
Fallout 2 had fucking :warf-wtf: in it, not to mention numerous other examples of sci fi and horror convention regulars you'd see pop up in PC games of the era
Answer for Asia/Eastern Europe/Latin America games: Not many people spoke English and it was rare to find someone who spoke without an accent. They had to get random Anglophonic people they knew. Most of the time, the script was translated wrong and the "voice actors" didn't care.
Answer for American/Western European games: They didn't have enough money to pay for good voice actors, so they used some staff members as voice actors.