Grill growth is a function of marketing. This is based on peoples' (at least a statistically significant proportion of them) perceptions that bad-ass trucks have big grills like big rigs.
If you've noticed grills on big-three show vehicles over the years, they're often even more extreme. RAM started this trend in actual product. At the time, one of their marketing honchos noted that it was controversial with half the public loving them and half the public hating them. But, he noted, appealing strongly to half the public would significantly grow their market share (which was abysmal at the time). It worked. Anyone who doesn't like the great grill look needs to blame the tastes of your fellow mother-truckers.
Grills generally aren't part of the crash structure. In fact, one of the pickup-related road safety issues is keeping the bumper and other crash structure bits and bobs low enough to engage same on automobiles.
As a side note, for a while stylists were ridding cars of their grills. That reached its height when Infinity first came to market, with a grill-less sedan. The market rejected it, which slowed Infinity's growth for years. The rest of the automakers saw this, and responded by growing their grills. If you look at the grills on a new car, many of them have sections that are fake. That is, they look like a grill, but the dark areas are black plastic, and simply serve as a faring to push air over the top of the car. I haven't looked closely at truck grills for a while, but wouldn't be surprised to see the same.
Carry on.