Why are most fixed height desk legs so high?

Everywhere I look fixed height tube style desk legs are at least 70cm/27.5" high, sometimes even higher. Once you add a decent thickness desk top (~3cm) suddenly your desk height ends up being 73 - 76cm high or around 29 - 30inches in some cases.

This is the case with all those people using the Alex drawers as legs.

You end up needing your chair so high that your legs are in an uncomfortable position unless you get a foot stool.

Even most standing desks seems to have a minimum height of 67.5cm

I'm 185cm/6'1, so I'm not short, but these heights just seem too high for comfortable use. I can't imagine how most normal heighted people cope with this?

Am I just sitting wrong? What's up with this?