I think it's a little too easy to be critical of the errors we find in the movies. Movies, in general, are meant to be entertainment and, at most, approximations of actual events. As such, the materials and props used don't necessarily need to be 100% accurate as long as what is being used is representative of the flavor of the times.
Add to this the basic fact that WWII German (and US) battle equipment isn't just laying around waiting to be used in the occasional movie or TV show. True, there are companies that stock this type of equipment but the rental fees and useage limitations often preclude their use in the ways that a director might envision. Say a director wants to film a tank battle between 12 M4s and 15 Tigers. Where the heck would he find this many operational tanks? Even if he did, would the owners allow such things as blowing the treads off with explosives or setting off a charge inside the tank to blow the turret off simply for cinematic effect?
Today, many scenes are computer generated but in the past many military vehicles were destroyed for our entertainment. Think about how many Jeeps you've seen blown up, burned up, crushed by tanks, rolled over, etc. Each one of those is one less that's available today. Assuming that the amphib Jeep in the Arizona Jones movie was authentic, it was destroyed and isn't available for the next movie. Likewise the tank that went over the cliff.
As much as we'd like to think otherwise, the M37 is a pretty unrecognizable vehicle. Most people simply wouldn't recognize it as wrong in a WWII setting. The same goes for the various flavors of deuces. It's one thing to recognize errors, but don't be too harsh in your criticism.
Finally, if a movie company approached you and asked to rent your M37 for a movie, would you do it? Remember that they often want to modify the vehicle by cutting holes for camera access, or drill holes to mount external cameras. Also they might think it's no big deal to run it into a tree or another vehicle, or roll it off an embankment onto its side.
Of course you wouldn't. The same goes for owners of authentic period equipment.
