Like everything, it depends
If you're selling locally a serviceable bar and new chain will make it easier to sell to any homeowner / non-CAD infected potential customers. To most people on this site no B&C is an opportunity to use up stuff that's just been hanging around. Someone looking for an affordable alternative to a new saw to clean up storm damage or cut a few cords is most likely looking for a turnkey saw. In these situations. you'll need a B&C for demo purposes anyway.
The few saws I've sold have been local, ftf transactions and always included a nib chain. The chain on the saw is usually more than 1/2 gone but sharp. Learned the hard way 1/2 the people showing up to try the saw don't have a clue and if given the chance, will ruin a new chain and not buy the saw because it cuts lousy.
If you're going to ship, no bar is certainly much easier.
Take Care