Lens distortion (also called "barrel distortion") is not what causes parallel lines in reality to appear non-parallel in a photograph
Barrel distortion causes straight lines near the edges of the field of view to appear bent...
... and it really only applies to wide angle lenses. I would not consider the 53° field of view of the Apollo lunar surface cameras to be "wide angle"
I'm going to nit pick a little here... Given how perspective works, any 'straight' line that is
not the one you have centred in your field of view (be it your eye or *any* lens) IS curved. The further from the centreline* of your field of view, the more curved it is.
For both lenses and your eye, it is relatively easy to correct this effect IF and ONLY if your field of view is limited, eg out to about 90 degrees f-o-v (that figure is highly arguable). In lenses, the barrel and pincushion discrepancies are what are left over from the designers choices on how to create a rectilinear lens, ie one that corrects for the actual, real, not illusional, bending that happens for everything above/below (and left/right) of the centre of view. As Smartcooky said, it is normally only a problem for lenses that are very wide angle, but that is *only* because lens designers do devious things to twist the image into a roughly rectilinear form when it is projected onto the sensor/film. Once you get to the very wide (fish eye) lenses, they basically have to give up and accept that it cannot be done.
Interestingly, for those of us who do panoramas by stitching lots of images together, this rectilinear correction probably creates more trouble than it solves.. and we have to learn about this stuff as the perspective issues become quite problematic. We have the inverse problem that mapmakers have, as it were, when they have to flatten the globe. Think about it..
Your eye has an easier job of it - the eye
does actually see a very fish eyed world, but you have a brain that takes care of that and straightens everything in some very, very clever ways. It sort of *has* to, as you
know the lines are straight, and they shouldn't bend.. so the brain simply makes it so...
This perspective issue, which is simply caused by us being effectively a single point in space around which a spherical universe exists, also explains the Moon Tilt Illusion (it's not an illusion!) where the Moon can be (and often is) clearly illuminated from way above the horizon even after the Sun has set, also anti- crepuscular rays, also the way railway lines bend outwards under your feet and then converge at the vanishing points. Straight lines CANNOT do that, yet they do -
from a single point perspective. Anyway, I have a bit of a bee in my bonnet about this perspective issue - at BAUT long ago I largely unsuccessfully argued this, and some erudite members there (Hi Grapes..) pretty much ran me off the thread, wrongly claiming that straight lines must always appear straight.
It's a bit offtopic, but I'm very happy to elaborate in great (painful) detail, including a pretty simple elegant mathematical proof (all you need is you standing near a fence, and some trigonometry...) If this subject interests you, see
this link from someone else who gets it and explains it well using the moon tilt thing...
* I've done a bit of simplifying here, I hope any perspective purists will forgive me for trying to simplify.