The point was that it’s pointless from the point of view of the sender. It’s always annoying and pointless from the recipient’s side (Except for those idiots who actually think they’re getting good offers).
But the spammers don’t do it for fun, or out of malice, they do it for profit. The links usually point somewhere giving you a way to give money to the spammers by buying something from them (or by them scamming you). That’s the point of sending spam, from the sender’s view. But if the spam message doesn’t provide any way for the spammer to make money out of it, well, pointless.

And yes, that acronym is pretty fitting, even if it’s only a retrospective invention and not the original meaning.

Stupid
Pointless
Annoying
Message

It sounds stupid, pointless, and annoying. So in the general meaning of the word…it adds up.
Goodbye,
Int-Bum