There is a significant weight saving with thin spokes such as DT Super Comp (triple butted) or even thinner DT Revolution. Weights range from 444 (straight) to 283g (rev) for 64 DT spokes.
As a lightish trail rider, personally I would rather have a full set of traditional spokes but use thinner ones, than pay silly £ for a custom wheelset with far fewer spokes and questionable serviceability. I use Super Comp spokes at the moment, they let me use a slightly heavier rim than the 717’s I used to run but still have a lighter overall weight.
I’ve known plenty of people who are quick to suggest anything thinner than double butted is a potential hazard, but then they go and buy a custom wheelset with hardly any spokes in it, that has to go back to the OEM for repairs. An old v-brake set of 517’s/XTR hubs/DT rev wheels lasted me well over a decade of regular use including trips to the Pyrenees and other similar places with no maintenance at all – probably my best ever wheels, shame they were V-only…