I draw the line at boxed and box-boxed, but I am keeping an eye on the protective covers, often the lenses and cameras come without them.
This is an area where I am blessed, seeing how my system came with a number of OEM darkslide, and back plates, plus at least one or two camera 'corner peek hole' plates.
The 50mm, 150 and 500 that I've bought over the years and the F series 2.8 50mm I was given for a parts/practice repair lens all had the front caps, and I believe at least three have lens caps, though they remain with each lens.
My friend that gifted the System to me believed, as I do, that having spares is crucial in the field, as, for example the lens back cap might just be blown of a car top or a wall, etc, into that dimension where washer/dryer socks go, never to be found again, on a windy day or by traffic.
I'll still buy or trade for a Lens Cover or other spare kit piece, when I see a deal in an area I want to be prepared for, like the 500 "V" body level for sale now, which at the moment, is out of my budget, or the lens hood mounted flash shoe, or a spare Rapid Tripod Mount, as these pieces are very likely to go walkabout when photo road trips, as my last long weekend trip demonstrated, while trying to make a shot, that required the rapid release, which I was unable to find.
Finding it required a search that discovered it in a completely wrong packing bag.
To me, that piece is a good example of kit I do not want to leave on a tripod or monopod, nor the camera, but use often enough to be part of my mandatory field kit.
Onice acquired, I won't trade or sale a spare, simply because of the difficulty of finding and needing duplicates, in the field or online.
If you run up on an affordable piece. grab it if you're able. You never know when it'll come to be critical to your next outing.