It's due to the shift in society, it takes a lot more to shock people nowadays than it did in 1997.I think my problem with the recent sexualization issue is that it seems to have grown. DOA1 started with the bouncing breasts and the nude Kasumi in the intro, but that was about it. DOA2 and 3 were limited to promotional materials. However, the ads for DOA3, the "She kicks high" campaign saw a shift in the marketing, made even more explicit by DOAXBV's "tissues sold separately" ad and the many skimpy bikinis in the game.
DOA has been banking on shock value since day one.