Why tf are they using IR guided missiles instead of unguided missiles especially for close quarters and if you're launching that quantity of missiles, IR guidance systems are a waste of money, in addition to that the space pirates should be leading(shooting where the target will be instead of where the target is) their shots
Unguided missiles in a space battle like this would be as useful as a dogfight with unguided missiles—that is, useless. We've been using heat-seekers since the 50s because without seekers or radar it's better to use canons in a dogfight and impossible to hit anything at range.
Heat seekers are at their best when in close combat, as there's less time to lose track/get distracted by flares. Also, 2 things to keep in mind:
1) Infrared seeker heads would be ancient tech at this point, and cost very little compared to what they cost today. Spend an extra 1k per missile to make them an actual threat? Easy decision.
2) The pirates only seem to use them in defensive battles, not when they're pirating. Even if they do, the cargo they get probably costs more than the missile they used.
The missile the MC fired was a special anti-shield, anti-capital ship missile, and it only cost half a million, which is way cheaper (I think 1/6th) than the the cost of today's best anti-ship missiles IRL.
A modern AIM-9X is $381k. Adjusting for inflation, an AIM-9B (1956 variant) is 40k. Considering how there's space ships and artificial gravity, heat seeking systems would be cheap.
So maybe that helps put things in perspective?