I don't have any idea.
One idea I'll throw out is that if a pilot already in a right turn sees
a conflicting aircraft ahead of him, he'll already be deviating to the
right since he's in a right turn pattern. If he was in a left pattern he
would have to switch to a right turn to avoid the oncoming aircraft if
they were approaching head on, since both aircraft are supposed to turn
right to avoid a head on conflict per the FAR's.

JPH

Roy Smith wrote:
It has always struck me odd that a standard landing pattern is left
turns and a standard hold is right turns. Having a left patterns for
landing makes a bit of sense, since the pilot is on the left side of the
cockpit and has a better view of the runway making left turns.

But, for IFR holds, there doesn't seem to be any advantage to one way or
the other. Why did they pick right turns to be standard?