It matters if the seller lists something as "new" and prices it accordingly.

Whether the presence of the original shrinkwrap means it's new or not, can be debated.  The plastic used in the 60s and 70s could deteriorate over time, and be more easily split, torn, cracked, etc.  So you could have a kit that is otherwise untouched, in its original box.  It wouldn't be mint, but would it still rate "new"?  "Like new"?  You can descend into debates about the minutiae of rating items for sale on the second-hand market.

You have to ask yourself what your motives are for buying the kit, what you want to get out of it.

I went through the same phase, when I got back into modeling some 20 years ago.  I wanted to buy kits I built as a kid.  But I didn't care about the packaging, or decals, only the sprues.  I knew I could source new decals, to replace old, aged ones.  And I don't need the boxes.

But I know there are those who want the boxes as well as the build.  And then there are those who just collect kits.  And I don't mean those of us who have accumulated a stash, though we're accused of being just kit collectors, not builders.  I mean people who collect models, just as people collect anything else.

I belong to a couple of Facebook groups devoted to this or that brand of models, and the collectors are well-represented.  And they'll pay prices far above what I would, for an old kit, with its box.