FCS has nothing to do with ninjas or malls. As mentioned already, in at least one post, they are helpful for those using optics that cover the rear of the slide, and for those who prefer them for a chamber check. I remember when they became fashionable, and for many, today, that is what they are, a fashion statement.
If I ever order a Baer, built to my specs, perhaps as a retirement gift for myself, it will not have FCS. If I buy a Baer from a dealer, and it has FCS, that is OK with me, too. My Thunder Ranch Special has FCS, which do not bother me.