Since the lock mount is often just a cut-out in the laptop case, the result of theft is typically a cosmetic but non-functional blemish to the device.

Mind: anyone receiving the laptop would have a strong indication it had been stolen. This might or might not be a concern.

Additional deterrence? Sure. Proof against theft? No. Slow down an opportunistic smash-and-grab situation (I've seen ~ $20,000 of hardware stolen inside of 60 seconds)? Sure.

"A lock keeps an honest man honest."

I guess it depends on the laptop. The last time I used a lock was with a pre-Retina MBP; short of cutting the cable (doable but you'd better come prepared) or what it's attached to (ditto but probably harder) you're not getting that off without a fight.

An angle grinder and/or drill can do wonders. If you can snip the cable, you can remove the lock head at your leisure later.

This still slows down the casual / opportunistic thief markedly, of course.