Most of your conversions are incorrect. Looks like you also need to brush up on your measurements. Y'know, to help out those guys on the phone. Might even save you some shipping charges. ;)

If I'm wrong then please correct me and give me a couple examples where your corrected measurements are applied in the real world. I work with both measurement systems every day so please...correct me.

When referring to my 18 cm cock...sounds better than 7 inches...

Most of the world uses metric, yes. Liberia, Myanmar and the US are the only holdouts. Language follows at a distance as per usual.
The bald eagle is still called a bald eagle although the name was acquired when bald indicated 'white' rather than 'hairless'. Imperial measures are obsolete and should be recognised as such.

I dunno... as a female 18 cm sounds a whole lot worse to me. i think maybe in this case, inches is sounds more generous than centimetres...

As a carpenter, I use imperial and almost always have on job sites, as does everyone else. I would never buy a tape with both metric and imperial as they are just annoying.

However, in the apprenticeship schooling, the building code is pressed a lot. The building code is all in metric. so a 2x4 is a 38x89 mm or something like that. All the specs of structural building and nailing schedules, stair codes, all in metric. Pretty frustrating the disconnect between the codes and what is actually shown for the most part on drawings and used with everyday tasks.

just depends what you're used to..

When talking to anyone outside of Canadians who know both or Americans, nobody knows what the hell 7 inches is. When I speak to an Aussie or any European they have no clue what I mean.