When I was doing enduros we used to get lots of rides on the local army ranges which were pretty much all sand in one way or another so I used to buy chain by the roll.
With chain I've bought pre-cut I've often found that it's a link or two too long, when I was a younger and more trusting soul I did fit and rivet one of these once. It was flappier than the knackered one I'd taken off, oh
joy and
bliss thought I.
These days it's mostly just pre-packaged to specific lengths for what is popular or common.