"If i look at recent wars the need to disguise a single tank is not there. On the contrary. Usually putting a tank somewhere has been a show of force. The typical IED rigged on the roadside will not be operated by somebody having a infrared optics, sitting 2km away in a cold-war style observation vehicle/plane, but somebody with perfect visible light view on the vehicle."
You are looking at todays asymmetrical conflicts where western powers fight 3rd world armies and guerilla armies. These armies have no real capacity to take on western armies in conventional warfare. And they are not really a military threat against western armies and societies in terms of their capacities for destruction. Let me illustrate this: In Iraq the coalition has had a total of 4800 military fatalities including accidents while there have been 2700 coalition military fatalities in Afghanistan so far. These two wars thus add up to 7500 coalition military fatalities so far.
Compared to major conventional wars the casualty rates in these conflicts are therefore simply insignificant. Your suggestion is to use (most of) the limited military development resources on saving a few hundred or thousand extra soldiers in such conflicts. My view is that the main weight must be on preparing for major conventional (and nuclear) conflicts in the relative near future (~15-40 years). The likelihood of such conflicts is of course much lower than Iraq/Afghanistan type conflicts. But the expected casualties can be many orders of magnitude higher. For example a future conflict between western powers and a modernized Chinese military might only be won (or lost!) at a cost of several or maybe tens (or in worst case hundreds) of millions of fatalities in the west.
Now, I am not a warmonger but I do believe that peace is best kept by a strong military alliance of democracies. Or as an old Roman saying goes: If you wish for peace, prepare for war (Publius Flavius Vegetius Renatus in De Re Militari).