[riffraff]

I think the designers just didn't think of it.

Women also started with a feminized version of the uncomfortable device and then switched to diapers, and then men followed.

It's possible there were no women on the design team but I don't think it's a case of bad masculinity.

[darkwater]

I don't think that having or not having women in the design team is the key here. IMO it's more about how men perceive how men should be.