It’s common to work as an assistant as part of your development as a photographer. Not only will you learn, but if you get a chance to work for a famous photographer, you will be tainted (in a good way) by their name. This can in a very real way improve your opportunities. Particularly at the high end of art (as in real art that hangs in real art galleries) and fashion photography.
As in other lines of work being familiar with the “industry standard” is often critical to getting a job and getting a job is a stepping stone to doing your own work.
So the “industry standard” argument unfortunately hold for photography as well. At least if your aim it set high. If your aim is set even higher and you are confident enough to drive your own path you can do as you please.
None of the above should be seen as me condoning the state of affairs or suggesting that anyone use LR.