I think you are assuming that the time and cost involved is trivial? And all for spreading goodwill to a relatively small number of geeks who care about old, abandoned software?
Goodwill is nice karma but somebody has to pay for it. Businesses are not charities. It really is not realistic to think of them as such.
Nevertheless, some developers/publishers do release older software for free.
You are addressing the specifics of why that is not profitable and I'm addressing the principle of goodwill and the respect it engenders when shown. No, businesses aren't charities but it is not beyond the scope of good business practice to engage customers and promote the brand without making an immediate profit.