Channeling cable into blockwork- conduit required?

[foodie]

Having some building work done was talking about where wiring is going etc.As my dad was a sparks (now retired), I fully expected for it to be done how my dad would have done it- wires into pvc conduit and then ready to plaster over

However, the builder says that's now unnecessary and that once the cables into the channel, they are fixed and then it's just plastered over.

I'm not sure whether times have changed or the sparks will just be doing it because it's cheaper/ easier?

Collective thoughts from others would be appreciated.

Thanks,