Garland,
It may be that they just SEEM wider.
Look at Oakmont. It would seem fairly narrow in 1985. But today they seem much wider, due to their fantastic tree management program.
As some newer courses still seem to fall victim to the "landscaping" or "beautificaton" efforts of screwed up green committees, their apparent width shrinks.
Some here have propsed that even the great Pine Valley has fallen victim to tree growth. But this picture from SI in 1958 would seem to suggest the tree "issue" existed 50 years ago too:
