At some point the webpage says something like "You are deeper than the Mariana Trench" and also make a few jokes with other comparisons. I expect USA people to prefer to avoid SI units.
If the site where showing temperatures °C and °F option would be even more important. I can translate from feet and miles ($feets/3 and miles*1.5) and get a good estimation, but I can't translate from °F to °C in my head and know if I must use a hoodie or not.