>>64124955
I think it doesn't suit the vibe or lore of the marines.
They might be pretty gung-ho and kill-focused but they're not death seekers per se.
It's kind of a Zealot ability but Protoss don't use mines do they?
Zerg as a faction are not very defensive and don't use mines either, and Zerglings have burrow so they are the mine.
Zerg would be more building a unit that has its only purpose to soak fire to protect other more valuable units and dying, deploy something offensive that seeks on the enemy. They're just not that defensive.
Protoss make the most sense I think, I'm just not sure what a Protoss mine would look like.
Maybe it turns the dying unit into a probe with a command detonation.