WEll, a lot of classics are not copyrighted, AFAIK,
but I am talking about boardgames classics here.
Stuff like Chess, Draughts, Go, Hexxagon, Game of Life,
Awele, card games, and so on, and so forth...

As for abandonware, it depends which games, but if you
frequent abandonware sites, you will realise that some
games have quite a following.
One of them (which I follow myself) is Darklands, which
was released around 91. You could look it up and its
fan website to see the effort that went into reviving it.
Sometimes the authors actually answer and express their
gratitude for the support, but most often the real problem
is that the author is not the one who own the game, hence
they cant decide to allow you to make, say, a sequel.

The Hasbro effect, shall we say... some guy got money,
buys the rights, and anyone else who dare say anything
gets sued. I believe there is/was a similar problem with
making a LotR RPG because some company had the rights but
didnt want to release them, but neither wanted to invest
any money into making the game. Effectively creating a deadlock.

Fucking capitalists, IMHO.

Sancte Isidore ora pro nobis !