Dye-transfer prints are very hard to duplicate, too. I think studios only do it if they absolutely have to. I know several 2-strip Technicolor films only survived as 35mm Technicolor prints. I'm fairly sure the surviving deleted material from For Whom the Bell Tolls only survived as prints. Thankfully, most 3-strip Tech films exist with complete camera negatives. At worst, some (like all pre-1950 MGM cartoons) exist as 3-strip positives.