Companies upgrade obsolete or surplus equipment and yes, sometimes go out of business. One way or another, equipment will either get sold or go to the scrapper for its value in recycle metal, etc.
I freaked out a couple of years ago when one of my clients sold three 316 stainless tanks (500, 4000 and 10,000 gallons) for scrap metal. I could have put them in contact with an equipment reseller that easily could have gotten them 20 times the cash. Stupid bean counter wanted to have his balance sheet nice and clean though. By the way, the bean counter was fired a few months later.
Not to brag, but before my company hired me, we would regularly pay the trash man to haul away materials no longer in use by the dumpster or even the truck load. Now, we get paid for it or, at worst, get it hauled away for free. And equipment which we consider obsolete is often considered leading edge in places like Brazil or Indonesia.
It isn't always easy, though. Sometimes, the bean counters get really irate when I don't have a buyer found within their artificially imposed deadline and even places like Loeb won't take everything.