The amusing thing is most times they don't really make best use of it by repeating things that are in the SID, sometimes repeating everything that's in the sid.
This happens to me a lot too, and bugs me every time. Heading south out of one of my home airports (PWA), the usual SID is the MUDDE THREE.
https://skyvector.com/files/tpp/1911/pdf/00739MUDDE.PDF
I will get a clearance of "Cleared to XXX via the MUDDE THREE departure, XXX, XXX, direct, maintain 3000, expect 9,000 10 minutes after departure, departure frequency will be 124.6, squawk 1234." And usually somewhere in there "on departure fly heading 201".
That's just repeating the SID. One of the main purposes for SIDs is specifically so they don't have to say all that.
So they could just say, "Cleared to XXX via the MUDDE THREE departure, XXX, XXX, direct, squawk 1234."
I can only imagine, though, that if they did that, so many pilots would ask "what frequency do you want me on?" and other similar questions, causing ATC to have to say it anyway. I should ask the controllers next time I talk to them.
Assuming that's the case, it's a training issue. SIDs and STARs have never been emphasized in training as much as they should. When I think about it, every time I file IFR down into the DFW area I fly a STAR. But most of the time I don't fly an approach (because it's VMC). So they should be given more time in training. As an example, this guy probably was just never trained on SIDs: