Let's break this down a bit, shall we?
This would imply that martial arts started out as something other than fighting methods. Historically, the fighting methods came first. Over time, some (but not all) martial traditions developed various philosophical trappings (or at least paid lip service to same), sometimes at the expense of the original fighting utility. Where are we today? Some martial arts schools teach just fighting methods. Others teach deeper philosophical/moral lessons as well. Still others give lip service to a philosophical creed while actually doing very little to instill that creed in their students. In other words, this era is pretty much like previous eras in the martial arts.
I'm all for a rigorous academic approach to historical investigation, but how does this apply to martial artists in particular? Martial arts history has typically been passed down through oral tradition and has long been filled with tons of distortions and fabricated nonsense. Thanks to the internet, we actually have access to much more accurate details of martial arts history than was possible back when I started studying. Even so, many aspects of martial arts history were never well documented at the time and are now the province of speculation unless a trained historian with time on his/her hands manages to investigate and find new information.
Which martial arts are you specifically speaking of here? Some martial arts schools are aimed specifically at children - that would be their function. Other schools don't even admit children. Some issue black belts to teens. Some do not. Some don't issue any sort of belt to anyone. A rank belt is meaningless except in the context of a the particular system where it is issued and can have different meanings depending on who is issuing it.
This does sort of sound as if you are calling out particular posters without having the courage to name names or specify your complaints. On this board we have representatives of many different arts. We have people who have trained for a few months and others who have trained for decades. We have some who don't even train in any art yet and have come to ask for advice on selecting a school. We have folks with all different reasons for training - some for self-defense, some for competition, some for cultural expressions, some for fitness, some for fun. Among these members you can find all levels of "scholarly and philosophical development" and that's probably as it should be. BTW - when did "scholarly development" become an expected attribute for a martial artist?