Why not ban assault rifles?

I cannot understand why this country allows citizens to buy assault rifles. Is there a purpose for these guns other than killing a lot of people as quickly as possible? There is clearly no skill or marksmanship involved in their use. They can't be legitimate hunting rifles. Other than politically appeasing the NRA and making gun manufacturers happy, can someone provide a rational explanation why this country should not ban the sale of such weapons?

Rich Farrington

Hesperus