Do large public companies ever "quit while they're ahead"?
Assume a company decides to "wind up". What would happen? Its competitors would want to get hold of its tangible and intangible assets (like customer base, patents etc). How is this different from "fighting to a buyout"? In this second scenario, the company has always available the option/threat of continuing competition (possibly harmful to the competitors), while in the "wind-up" scenario it does not -it has committed to leave the business. So "fighting to a buyout" gives the company better position in negotiations, and so chances to increase its selling price compared to the "wind up" scenario.  

You could spice this with theories about management, and how "management will not let go" etc, but the above provides an interpretation that appears more widely applicable.

Compared to smaller companies, large companies have more market power and so the "threat" of continuing competition weighs more heavily with competitors.