All of the larger telcos and power utilities have been 're-smelting'
copper for decades. Verizon (nee NY Telephone) had a copper smelting
plant on Staten Island at one time that recycled all of the used
cross-connect wire and cables removed from underground and poles. Telco
main distribution frame personnel were, and very likely still are,
instructed to use "copper-scrap" bags for depositing small bits and
pieces of copper wiring collected at cleanup time at the end of work
shifts. Many years ago, copper, for this reason, was one of the three
"C"'s that no one would mess with. Copper and Cash were two.I'll leave
the third one to the reader's imagination.
This subject is interesting because it's one of the cost-justifiers in
business models that seek to re-engineer large office buildings and
other copper-intensive venues where the objective is to replace all
copper wiring with hybrid fiber-wireless alternatives. While
reclamation through salvage is only a by-product of this movement, it
is nonetheless one that is cash intensive, so it cannot be overlooked.
Not only is the copper data cabling removed (Cat3/5e/6, in this case),
but also potentially tons of power cables and racks supporting
sometimes hundreds of riser telecom/LAN closets, where there are
usually anywhere from two to four closets per floor, depending on the
size of the floor plate, in a forty- or sixty-story building, say.
Every copper penny helps these days.
I know of a guy that was terminated for "stealing" CAT5 that he was
instructed to throw in the dumpster.
Jeff
It's pretty standard for any company to terminate upon taking something without permission.
I worked with a company that threw away / recycled nearly an entire 100k sq. foot datacenter. All of the gear still in working order. It's just one those things...
Your employer tells you to throw it away... It's best to throw it away and not try to take it home 
We (employees) could request specific pieces but the majority was thrown out. Kind of crazy to see entire Cisco lab environments trashed but it's not uncommon and trash or not, still stealing.
As far as the original question:
More companies recycle and properly dispose of equipment than they did ten years ago. Yet, if they aren't being looked at to be "green" or something along those lines then many choose the cheapest route (the dumpster).
Per the note by Jeff, it's not recommended to try to take it into your own hands. Your best bet would be to approach your employer with a recommendation that you feel may be more cost-effective or environmentally friendly.
The amazing thing is sometimes they will pay to have it trashed instead of the option of a recycler/reseller coming around and picking it up at no cost.
As you said, it's just one of those things.
There are constraints beyond the logic of "common sense". And it flows from the accounting department
A former employer had a bunch of old PCs replaced. The old ones, for "tax reasons", had to be destroyed. Which meant they had to go in the dumpster. What happens to them after that is not my concern; I won't even notice if they aren't in there when the truck comes to empty that dumpster. Do what NCSU's ACS ("the hall of records") used to do... post to the news groups when ever they had anything "interesting" to throw away.
In today's world, throwing a computer in a dumpster (headed to a landfill) is illegal just about everywhere. esp. CA.
--Ricky
The cables might still have some ultra-secret bits in them.
Assumption: Construction guys are present.
1. Dump cable in large pile on the floor
2. Yell "Does anybody want this copper?"
3. Use broom to fend of multiple takers
4. Tell the guy who wants it that he can have it as long as he hauls it away
Not that I've ever done this of course...
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