Rifle trigger guard

[Nhgrants]

Is there a practical reason that a rifle trigger guard has the added trail under your
3 fingers of your shooting hand? Is it a way to provide a bigger grip without making the wrist bigger?
Or is it just looks and style?

[54ball]

 You must be talking about the large grip rail on some Lancasters and VA rifles. I think it's a matter of style more than anything. I actually prefer the grip rail to "kiss" the wrist and either turn back in (like a Gillespie) or slightly outward like Lebanon or some Dickerts.
Untitled by Travis Brown, on Flickr

 If the style calls for it, I'll build one with the tall grip rail but I sure do like the feel of a rifle that's grip rail comes up tight to the wrist.

[Mark Elliott]

If I understand your question correctly; it is why is there a grip rail?  The grip rail is there to help you pull the butt stock into your shoulder.    Some grip rails do this job better than others.   On my S.W. VA rifles,  I point the grip rail spur toward the muzzle to help is pulling the rifle back into your shoulder/arm.

[bgf]

Especially with a stepped wrist, the grip rail spur turned back towards muzzle (as Mark says) or even just straight down more or less functtions a lot like a pistol grip for me.