Probably because the metal razor blades fell out of fashion first. This setup doesn't work with throwaway razors and mach 3 pro extra plus whatever systems.
I recently got into shaving with a safety razor and I don't know why I ever bought expensive 3 or 5 blade heads from gilette or whatever. Despite what some enthusiast shaving communities might make it out to be it's really no more difficult using the single blades and it's way way cheaper.
Gillette knew stacking more and more blades would bring out some primal urge in men. They saw their pals rocking 3 blade heads and knew they must get the 5 blade version to one up them.
I think I remember a (SNL?) sketch from back when 2 blades were the norm and maybe there were some 3 blades starting to come out with an ad for like a 17 blade product.
I tried it a couple of times and my face got torn up something awful. I switched back to the Gillette multi blades, but now I take care of them and dry them well. I have sensitive face skin but thick beard hair and it didn't like single razors.
Ah that's too bad. I have thick hair as well but I guess my skin isn't too sensitive. It also seems like it's a sharper shave than the multiblades, but maybe that's because I didn't use to change them enough bc they were so expensive. At least it's easier to get hair out of it when it's just one blade.
I used a single blade disposable once in a pinch a long time ago and I guess wasn't careful enough and cut pretty deeply into my cheek.
A blade tugs at the hairs before cutting them off. That pulls them out of the skin a tiny bit. The first blade pulls them out, the second grips them before they retract, and cuts them off lower. It makes a noticeable difference. The third blade makes a very tiny difference. After that, it's marketing. (Should I look up studies to cite?)
In my experience, electric gives the cleanest shave. In the long run it's cheaper, too.
In my experience I get a much better shave with a DE than a disposable razor. It's also much cheaper and reduces waste significantly. Cartridge razors are a scam.
I've never had an electric that feels good--maybe bc I have really thick hairs it always has some places that get yanked instead of cut. Cost wise I guess electric's pretty cheap in the long run but you can get single razor blades for about 10 cents so it's also pretty cheap