A lot of good points have been brought up in this discussion and I was happy to eventually see the "vanity slot" option be brought up. At the end of the day this is a game that takes samples of real life and distills them into bite-sized pieces of mind or eye candy for easier consumption. Being the owner of a game/comic shop this topic comes up now and again and you can generally see trends that occur as time passes. In presenting an idea through (to stay on topic I'll just refer to FFXIV though what I say can be true of card games, comics, etc.) the game many times an idea is reduced to something rather dramatic for conveyance. Most of the time when we are frustrated we may only physically get flushed cheeks and a bit of a scowl. That subtly doesn't get picked up well in media like this so we must also have the balled fists, a stomp, a huff-and-turn, or the like. Look at the /laugh command and just how "animated" it is.
So, actions and emotions aside, this translates to concepts of gender identity and conveying ideas that way so that they can be consumed easier without a lot of actual attention needing to be paid. Even earlier in this thread there was a good but lengthy post written that made good points. However, following it were a few "tl;dr" statements that proves that content aside the presentation wasn't suitable for consumption. When making an 8.5"x11" flyer for a club, business, or announcement you need to design it as such that you can convey all the information over the span of 2 seconds from about 6-10 feet away. Because that is our attention span regardless of gender. You need to get the idea across.
These comments are not including swimsuits, coliseum gear, or basic underwear as those are the exceptions to what we are discussing but at the same time exactly prove that they catch the attention of those who are running through town, etc.
As bards were brought up we'll compare them to white mages to further make the "quick distinction" example. All (standing) white mages look alike. It is a wall of white and red especially in the end of days. White mages are important, and I love playing one. But I was simply a face in a crowd and there was nothing exceptional or even slightly unique to break the monotony (something that, landscape-wise, was an issue in 1.x changing in 2.0). Switch to bard and it's a slightly different story. Yes, the shoulder reveal and the way the AF sits is different. It makes it different, breaks the pattern if only slightly. Dragoons, particularly female ones, with bellies shown. It is something slightly different that plays into a comfortable role our brains quickly filter for consumption and understanding.
This is the same reason why anime characters came to have wildly-different hair colors and why there are very obvious differences in builds because otherwise they'd look the same and you would have a lot harder time trying to figure out who is who (especially in senshi style ones). When the brain encounters effort it is only willing to put so much into it before you say "what" or "tl;dr". Not even the Green Lanterns looked wholly the same, nor Borg for that matter crossing into Star Trek because we can't handle too much sameness.
So the marketing and psychological distinction of it pointed out, it comes down to you, fellow players in how you decide to accept the content shown. One man's trash is another man's treasure. It is your acceptance and comfort level with how the game is presented that determines if you take offense to the developers or how other players may make ignorant statements. It is your brain and how much you allow it to take in what is presented. For most of us who play this game, as we are a community and there is context from the past and expectations in the future, it tends to be more comfortable to run around in underwear in front of other players. A real life presentation of this would be the use of the "n-word" among people. Why is it you can say that to your fellow nerf-herder friend but if someone you don't know calls you a nerf-herder you get offended?
Context plays a large part in the physical and mental intimacy and just how open we are to the messages presented by both developer and fellow player.