The ISML Necklaces were brought in to spice up the ISML regular season, and that still remains the case. A long several-month regular season could be boring without something notable happening at regular intervals, so I think it's good that we have the Necklaces. Originally, the Necklaces were awarded strictly on the basis of SDO (think of it as being like a Round Robin tournament in sports rather than the now more typical elimination tournament format).
Later on, they introduced the Necklace matches to spice things up further. However, they have always used SDO in the Necklace match results calculations. At first, voters didn't necessarily pay a lot of attention to SDO, and just voted their heart in Necklace Matches. But I do think this has changed, with strategic votes increasingly coming into play for Necklace matches.