You're joking, right? The NEC chipsets were only prefereable back in the days of the Optiarc AD-7200 series drives, and that was only for burning. MediaTek has always been preferable for those who want a more flexible drive that can burn, scan, and read well. NEC only burns well, but sucks at scanning and reading.
In addition, the main claim to fame of the AD-7240 series drives was their ability to burn dual-layer media. They were never as good at burning single-layer media as the older AD-7200 or the newer SH-S243 drives from Samsung.
Also, the other issue is the atrophy of the optical drive ecosystem. At one point, it semed like MediaTek was becoming scarce, and all the drives being put on the market were rebadged NEC chipset models. We can buy the Sony AD-7260 series directly, we don't need a bunch of rebadges. People are sick and tired of all these rebadges of the same drive. They're completely unnecessary and boring.
Rebadges were fun and important back in the day when you had the Nexperia chipset BenQ drives, but now, rebadges are killing the optical drive market.
So anyway, because most people already own one or more AD-7240 or AD-7260 series drives, they have no need for rebadged versions of those drives. They're redundant. It's MediaTek drives that have become valuable and rarer commodities now because they are harder to find.