Why can't blast weapons snap fire?

"BBDA Cleeeeeeeear...."

So this is bugging me for some reason.

A horde of Orks is charging. The choppas are swinging with murderous intent. They're only a few metres away, time for a split-second reaction only. The tactical marines fire their bolters and plasma-gun from the hip. They hope the indiscriminate hail of shells will kill an Ork or two.

And what does the dude with a missile launcher do? Whistles Dixie to himself while he carefully loads a krak round into his launcher, and tries for a headshot with an antitank weapon. What the hell, missile launcher dude?



Now, I get that firing a blast weapon at BS1 compared to BS4 is not a huge penalty, relative to firing a bolter at BS1 instead of BS4. But there are already different ways of snap firing - look at the way flamers do a flat d3 hits on overwatch. Even if they are hiding at the back of the unit, the charging unit is 11.5" away from the front, and rolls snake eyes on its assault distance, that badass flamer can somehow cook 3 of the little blighters. But the missile launcher? Krak or bust, buddy.

So why not use a similar mechanic, or make a hybrid? Snap shot a blast weapon, and roll a 6 to hit. If you hit, do d3 hits, or d6 for a large blast. Maybe if you roll a 1, you hit yourself (for kicks), although probably just once to keep the net payoff positive.

Surely it would make more sense (and be more fun) than having some of the most effective antipersonnel weapons around completely useless in the face of the onrushing foe? Or useless if they move? Even if its an overwatch only kind of deal. I could live with my shredder guy accidentally killing his mate when the Orks charge in, but surely he should have some chance of doing something with his area effect of infantry death!