LITIGATION
Really? Who is suing them? I would think having $250 million would make one a larger target for litigation than if one had $0.
That is exactly right.
Back in the 1970's when there was a judgment against them in the Polara golf ball suit -- later overturned -- the damages of $1.3 million, tripled, were more than the USGA had. That's when they got serious about stockpiling cash to fend off litigation.
Sadly, the more cash they've stockpiled, the more timid they've become about equipment rules, for fear of pissing off the manufacturers and potentially losing their nest egg. Whereas if they didn't have any money, the manufacturers would have little recourse -- if sued, they'd just declare bankruptcy and start over. [Of course, they'd need millions of dollars to defend themselves in the lawsuit -- welcome to America!!]
Also, of course, while the board of the USGA work aren't compensated, and just work for the perks, the staff of the USGA would be decidedly against sticking their necks out so far and not having that cash horde as a security blanket.