Interesting thing! Why did NATO use "improvised" armored cars in military operations in the Middle East? In the 40's and 50's, good 6x6 military armored trucks were created. They were designed from the beginning to carry heavy armor and heavy weapons. Paradoxically, such vehicles were in museums, and soldiers in Iraq or Afghanistan had worse, weaker vehicles.
It was designed at the start of the 80s when body army was light and semi-flexible. It wsa also meant to be a utility vehicle like a heavier jeep with a little armour and a roof. there were a few more armoured models for scouting but it was basically used for mobility and transport.
The Americans got into problems with urban fighting in Somalia (go watch Black Hawk down) then went into Iraq unaware of how much of a problem IEDs were going to be. The Iraqi army would be defeated, they would need light vehicles to police the liberated areas but otherwise they didn't expect heavy fighting, instead they got ambushes, snipers, IEDs, suicide bombs and intense fighting. they didnt have time to develop a new class of vehicles they had to improvise with what they already had by adding armour and guns.
They finally got round to introducing the Stryker which had armour, a proper turret and IED protection but it comes down to the regular problem armies go to war with what theyve got and what America had was support vehicles left over from an era when the soviets would have a front line and light utility vehicles would move the troops behind it.