I stuck with the stock front end on my '57 GMC for a few reasons:
I was pulling a 35 foot 5th wheel RV trailer a lot,and didn't find much that had the load capacity for it.
All the ifs kits I checked out would have lowered the front by at least 4 inches,and I like the ride height as it is.
Expensive.
I donn't want a cushy ride in my truck;if I want to drive something cushy,I'll drive my station wagon.
Simplicity;easier,and less expensive to work on.
Better ground clearance-a pretty big deal for me as I do a lot of driving on bad roads,or no roads.
It's all a matter of personal preference. I just happen to prefer my trucks to act like trucks.
Speed