Shooting long range is a lot easier with a bipod and sand sock using a properly zeroed scope than it is with irons and a sling.
Once the bipod and sand sock have eliminated the effect of the shooters heartbeat on the rifle, it is a simple matter of squeezing the trigger. Much less to worry about compared shooting with a sling.
This is why F Class scoring rings are smaller than High Power scoring rings.
The video game crowd is a lot more familiar with "sniper" style rifles than Palma style rifles, so that is where the love affair with the 338 Lapua comes into play. This may have something to do with why F Class matches have gained so much popularity in recent years. Can't say for sure though.
Machine guns are awesome until you have to carry one.