Now then, now then!!! Several possible reasons:-
1) Cockpit windows a bit on the small side on the Dak, and sometimes a bit delaminated
at the edges.
2) Pilot as misty-eyed as the passengers, knowing it all comes to an end in a few
weeks' time.
3) Looking across regularly at the other pilot with an unspoken "Did you hear/feel
that noise/rumble/vibration just now?"
4) Apart from the airmanship aspect of looking outside, spending a lot of the rest of the
time scanning the engine instruments, half expecting the flickering oil pressure
needles to depart from their normal numbers, closely followed in sympathy by a few
other guages besides.
5) Basking in the euphoria of yet another glorious flight when they didn't.
6) Wearing too-strong sunglasses to impress who-knows-which of the passengers.
Always assuming, of course, that the Guppy IS still there, and substantially in one piece.
Lest any of this should discourage anyone from taking a DC-3 flight while they still can, please don't let it. I've done thousands of hours on those very same aircraft, and I'm still here!
They're much better looked-after these days, and flown by some of the best and relevantly-trained pilots you could ever wish to meet.
(An ultimately sad and sombre thread; just trying to add a note of levity, if I may be so bold).