I can't pretend to know the specific reason why four bolt caps are used but in American V8's it's the high load engines that get the caps. Engines like the previously mentioned 350 truck engines, Ford NASCAR side oiler big blocks & SOHC engines, Chrysler Hemi's, I'm sure there's a Chev big block in there somewhere, & anything that needs to REALLY hold the crank into the engine block.

Keep in mind that the piston is trying to push the crank out through the bottom of the oil pan & the only think keeping that from happening is the bearing caps.

As the loads increase with climbing power outputs, regardless of whether it's a zillion RPM or some massive torque at lower revs, it is all derived from the piston pushing down towards the crank & it's just those poor little caps holding it in. The greater the power, the greater the push.

Some engines are able to produce so much power that the ability of the caps to maintain their shape & integrity is compromised.
The best way around it without casting a whole new block design is to beef up the bottom end with better quality cap material, stronger bolts/studs or bigger/ 4 bolt caps & any combination thereof. 4 bolt caps can help increase the rigidity of the block too if it's one of those flyweight 'thinwall' engines, but Hemi's wouldn't know anything about 'flyweight'.

As for your question about the lower reving truck engines, I don't know as the truck engine normally runs at a lower compression & lower power rating, so perhaps it's simply the hours of full load pounding that is enough to allow caps to deform enough to cause bearing wear problems or cap fatigue problems.
Passenger car engines rarely see full power at full load for more than a few seconds as the load is usually relieved by the spinning wheels or an increase in speed that allows a power reduction.

The A13 engine of Feral's produced it's best power at 10,200 rpm in 'endurance' trim. It uses billet steel bearing caps with only 2 studs/bolts to secure them. That's Datsun tough. ['endurance' & '10,200' rpm in the same sentence seems a contradiction in terms for most engines]

Click here for Ferals webpage on this engine.

This engine uses the "stronger fasteners & better cap material" method.