The dreaded twin and earth cable!
I has its place but I would avoid plastering it into the wall. You still need a box for the plug point/switch (or do you plaster that into the wall as well??)
The effort to use a piece of PVC conduit instead must cost less than R10…
I also much prefer to put in a piece of conduit (especially if it is a new build), mostly for future accessibility, but then it also has to be said that it isn’t the cost of the conduit that makes people do this. It’s the time saving. With conduit, you are essentially doing it twice, first the empty raceway, and then the cable in the raceway, potentially with some time in the middle for the plaster to set.