[@Lucidnonsense]

The fact that's you can find large amounts of natural and usable anti-matter only near black holes and neutron stars which does make them hard to extract from said places. And not only that, the matter of actually containing them and placing them in a weapon or a bomb. These two combined would make it very expensive. And since a single microdrop(microscopic drop) of antimatter(can't remember where I saw it) can power the entire energy needs of New York City for an entire day. Imagine a large quantity of anti-matter shoved in a bomb and you got an OP weapon.