It's definitely more popular and more visible than just a few years ago, but isn't part of the appeal the fact that it's NOT mainstream? Maybe that's just me, but the fact that our method of shaving is a bit of an anachronism means we're rebelling, even if just a little, against the commercial cynicism of mainstream shaving. If DE shaving went mainstream, that little act of rebellion would be meaningless.
For me Its Actually more of a graduation to the next level of personal grooming, Sure anybody can pick up a cartridge and get a decent shave, but this feels more like a next level thing to me a next step in being a man if that makes any sense to anyone else but me.
It is also a step back to a much simpler Time.
and perhaps a there is an element of "sticking it to the man" God knows i have spent far to much money of cartridge blades in the past and I'm not going to lie the money aspect has played a significant part in my decision to start Straight razor shaving. but ultimately there is a more "Manly" feeling to traditional shaving than in picking up a cartridge and just getting er done so to speak