On another day a couple gliders were in wave when a slug of moisture
closed the windows trapping them on top. One turned down wind and rode
the undulations to drier air in Maine and landed.

If the weather situation described is a possibility (which in this case it
was) and one possible outcome is to be left with no option but to bail out
(which in this it was), then why are pilots engaging in the activity?

Presuming this is a serious question (and not a rhetorical snark), a short
answer (no snark intended) is: because the personal rewards are worth the
apparent-to-Joe-Pilot risks.

A slightly longer and to-be-hoped more informative reply is noting that
sky/cloud conditions rarely change instantaneously over a sky volume in which
your averagely-informed soaring pilot ought to be (is?) paying attention to.
Thoughtful, comprehensive reading of earlier posts in this thread in which
atmospheric aspects of this day/incident are touched upon, make it apparent
that was (or seemed to me, anyway, from a wave-flying, glider-pilot-informed
self-interested distance) the case. I consider "overall atmospheric awareness"
(beyond merely staying up, I mean) a huge component of "general situational
awareness."

That said, there's no doubt in my mind - having been raised and become a
soaring pilot adjacent the mid-Appalachians and then done the bulk of my
subsequent (including considerable) wave soaring in the intermountain west -
that "eastern waves" tend to be "wetter" than "western waves," though some of
my most memorable western wave flights were "wet" buy local standards. In that
sense, for the moisture reason as well as additional secondary ones {e.g.
local geography and surface conditions) I tend to believe that eastern wave
soaring "generally requires" more incoming weather vigilance than western U.S.
wave soaring.

YMMV.
Bob W.