Well, first, I don't shave my head (I understood that as shaving the top of your head), so I will have to take you on that. Secondly, I believe that most people don't shave their head but their facial hair (correct me if I'm wrong). Thirdly, not all double-edged razors are paired with handles with safety guards - there are open blade handles; but even if you amount for safety razors, you still get more accidents compared to a 4-blade cartridge (they are designed precisely to prevent cuts).

Also, I fully agree with the price factor - they are less expensive, and as a bonus there is no plastic waste (at least in most cases, depending on the packaging of your razor blades). But that was not my point.

That said, I don't work for Gillette (or any related company), and don't get commission for saying any of this (this is all just 'IMO' type of comment), and apart from anecdotal evidence (I've had multiple conversations with people with 20+ years of shaving experience, using both 4-blade razors and double-edged razors, and they all, more or less, share my opinion) I can't really provide any data (maybe I could try to find some, but I don't care about this topic 'that' much).

I hope that this clarifies my previous comment.