And, again, it’s not about personal taste but about making people comfortable in the hobby.
Pin up art? In a calendar or maybe a novel cover, sure. In rpg book after book after book where the majority of female depictions in the books are chainmail bikinis? Maybe we really don’t need those.
Yes, there is a percentage above zero. For one, there's nothing wrong with sexy art when it's appropriate to the scene. If I have a picture of a tavern (to pick a rather random example) and it includes a singer on a stage that looks like Jessica Rabbit, well, fair enough. That's pretty understandable. Context matters.
But, when nearly every armored female character has boob windows and bare midriff, well, that's maybe not a good look.
No, it generally isn't a problem anymore.
Now, ask yourself WHY isn't this a problem anymore? Is it not because about fifteen (around) years ago, people actually stood up and repeatedly told the hobby that pinup art in the game was making thing feel unwelcome?
And, oh look. They pull most of the sexualized art from the game, and now, poof, 40% of gamers are apparently female. About two or three times the percentage from even ten years ago where women made up around 10-20% of gamers according to virtually every single poll out there.
Huh, funny how taking the stuff out that makes people feel unwelcome in the hobby results in those people joining the hobby in greater numbers.
All right so 15 years ago 2008 was the transition to 4e.
I am having some trouble coming up with examples of RPG books with the majority of women warriors being chainmail bikinis in the AD&D or 3e eras of D&D.
I can think of some Dragon magazine covers, some d20 era 3rd party Avalanche Press covers, but not a lot of interior art chainmail bikini types. Maybe some Mongoose publishing d20 stuff and White Wolf's more adult/mature oriented Exalted.
More often in AD&D there is a lack of female warriors period. In the 1979 1e DMG there is an unarmored woman in the woods (druidess?) talking to what looks like a party of armored warriors and unarmored spellcasters, there is the DCS recurring party with a woman magic user, there is a mermaid and a succubus picture, but no female warrior or chainmail bikini type. Similar for the 1e PH, there are only three women depicted in the art at all and none are chainmail bikini warriors.
1981 Moldvay B/X Basic however has iconic Morgan Ironwolf as the character creation exemplar as a prominent focus woman whose art is a fairly sexy warrior, but her chainmail is not unrealistic bikini type. 1983 BECMI has Aleena the cleric in full body armor.
Most D&D Monster Manuals have some specifically female monster types who are either attractive (nymphs and a number of other fey types, succubi, most medusa depictions) or generally specifically unattractive (hags, some versions of harpies) so there is often some sexy woman fantasy RPG art there but usually not ridiculous armor female warriors.
I might expect some sexy impractical armor female warriors in drow specific books given the BDSM decadent demon worshipping culture generally attributed to them and their focus on dominant women warriors and clerics.
Flipping open
WotC's 2003 Miniatures Handbook for 3.5 (I just bought the PDF recently so it is on hand) there is skimpy tiefling skirmisher armor for both the male and female tiefling art but with a ridiculous spiked boob bikini top for the women (cover and page 134) that seems to be evoking Warhammer Slaanesh daemonette types, there are two drow that can be considered borderline sexy impractical armor (pages 37 and 130), and the axe sister sketch looks like it has a bare midriff even if the accompanying picture of the miniature clearly does not (page 146), but there is a lot more art of female warriors throughout the book with head to toe armor even if it tends to the more fantastical than realistic (pages 4, 6, 7, 8, 15, 18, 22, 28, 30, etc.).
I think this is individual images standing out (such as Alias's boob window armor from the Forgotten Realms novel cover) more than an actual predominance of depictions in RPG book art from the 1970s to 2010.
I could also see this as more of a thing in computer games where constant visuals and limited designer provided choices are more of a thing than in tabletop RPGs.
Or are there examples of RPG books with predominant chainmail bikini women warrior depictions that I am not thinking of?