I have no LEO experience but I'd imagine increased mobility, decreased chances of rounds exiting the target and hitting an innocent bystander, and cost are the primary reasons.
Concerning over-penetration, that's largely a function of ammunition. Hollow-point rounds from a submachine gun don't (practically speaking) over-penetrate any more than those fired from a handgun.
If the concern is hitting something behind your target that you're not supposed to, over-penetration would actually be pretty low on my list of concerns about a submachine gun.
Though your comment is very much beside the point, I'm nonetheless left scratching my head.
Are you suggesting that submachine guns make you more likely to miss your mark? If so, this is spoken like someone with absolutely zero firearms experience, as submachine guns are much more accurate and controllable than handguns...
No I've fired a handgun and a fully-automatic submachine gun several times in the last few months. Accuracy on the first shot, sure. Unless you're on semi-automatic I'd be deeply concerned about uncontrolled misses on subsequent shots. Maybe the London police's MP5s are a billion times more stable in the shoulder than a MAC-10, but still - even with ample training I'd keep it on semi-auto pretty much all of the time, or 3-shot-burst at best. The muzzle rise builds fast.
You're being disingenuous by sneaking in the notion of long-burst fire. Your point about mussel climb and automatic fire is akin to saying "if you hold a pistol sideways -- gangsta style -- and repeatedly jerk the trigger, your accuracy will suck". Well duh! Use the thing properly!
Yes, firing from the hip on full rock-n-roll is less accurate than controlled shots from a pistol, though I should think that was both obvious and beside the point.
Carefully controlled shots from an SMG are systematically better-placed than carefully-controlled shots from a pistol. Full stop. Moreover, SMGs are so damn easy to control (again, assuming they're used properly, i.e. with the extensible/foldable/fixed stock) that you can trivially put 3-to-5-round bursts in a human torso at 5 meters. Anybody who can't do that has no business carrying an SMG.
Surely you'll concede than in just about any professional situation, full-auto fire is not used. Full-auto fire is a suppressive technique, and as such it is largely relegated to military action (and not with SMGs, by the way).
It is absolutely absurd to suggest that pistols are more accurate and more controllable than a firearm with a longer barrel and stock.
>> You're being disingenuous by sneaking in the notion of long-burst fire.
Not really. Try moving a fire-selector from safe to semi under stress and see how quickly you stop. Then look at the number of shots fired from fully-automatic weapons during police shootings. Then tell me long-burst fire isn't a concern when deciding where they should be deployed.
Curious if you've ever fired a submachine-gun on full-auto? You'll either rise significantly within a few shots or you're applying enough downward pressure to make it very unstable during recoil.
edit: Your edits to the above post seem to be repeating themselves and adding italics. Maybe I'll just concede the argument so you can stop hyperventilating at your keyboard. Calm down, seriously, for your own health.