I just got thinking why would you be at 16,000' over the CA Central Valley ?
I like to fly high, normally 8,500' is my min altitude while, I'm flying XC
around the state, but the oxygen requirements keep me below 12,500'. Even if
I had oxygen on board - I would probably not use it until I had to get to
altitude. For example, If you fly IFR than many of the MEA's over the
mountains are going to force your to have oxygen.

But say I was flying VFR, and I saw a line of CB ahead of me, I might be
tempted to push it and try to climb over them. Maybe, there is already a
layer underneath me so I can't get down to go underneath. Maybe, I just
don't want to be under a big mean CB build-up when it looks like it tops out
only a few thousand feet higher. Hopefully I have ox or maybe I figure I'll
be "over the hump" before I'll really need it. Either way I start climbing.
16,000' and the plane really doesn't want to go any higher, I've maxed out
the power, I'm pitched for best climb maybe a bit more and I'm still looking
like I'll enter the top of the cloud. I starting to get worried, maybe I'm
not IFR rated and anyway that is a mean CB cloud under me. I really don't
want to be inside it. Without realizing it, I'm dangerously close to a
stall. Maybe, I decide I've had enough and decide to do a 180, but as I
turn, the plane stalls. I wasn't expecting it and before I know it I'm into
the cloud getting kicked all over the place. Right about then I'd be really
glad if I had a parachute.