also mills would be confusing if you have say a 3.5-10x scope, they are set to 10x and you have it set on 9 or somethin, you would be off slightly in range calculation and you wouldnt even realize it
also 10x is fine for snipers at the standard ranges they would shoot the M24 at
SWAT snipers are on average 75m away, sometimes 25 feet, sometimes 100m or more so they usually go with an ajustable power scope so they can see targets very well at 100+m out if they have to, or not see a giant blur 15m away
also they usually dont punish thier equipment as much as the Army does, usually no need to drag it on your belly for a few hundred yards stalking the enemy in the field
Leupold is now producing some scopes with FFP, so the problem that Jeff is talking about with the mils only being set for one magnification wouldn't be a problem with those. Of course the majority of the ones made still have the problem of only working at one specific magnification setting.