Why not switch?
1. It's what we're used to. Metric system has been taught to children in school - even in the 'dark ages' when i was a kid. Perhaps with the hope that one day we might switch??? Although, whether we switch or not, it is very impt to know the metric system if one is involved in various scientific fields. It's still unusual to hear metric equivalents here in the U.S. (e.g. i'll often say it's 400m or 800m, or 3 'kliks' instead of 440yds/0.25 mi, etc. - do i ever get strange looks, even from my co-workers who also are familiar with the metric system, being engineers). Temperature is still my stumbling block, however. I'm forever performing mental conversions back and forth (unelss it's a common C Temp, e.g. 20 deg C, 25 C, 37C - can't think in Celsius yet. For years had my Audi automobile's climate control set for Celsius display (as a learning aid), but it didn't help much (mainly b/c it dealt with a restricted temp range, which i got to know well, but for OAT it was more difficult - maybe you can't teach this old dog any new trick (besides my wife hated having to always ask me to what number she should adjust the temp to - see case in point, viz. people are unfamiliar with it & resistant to change - in the interest of matrimonial harmony, my Audi's climate control system was returned to English units).
My daughter studied abroad in London, England & found to this day some people there still have some problems with various aspects of the metric system (mostly older people probably, but i didn't query her more specifically on this point).
2. Too expensive to switch, especially nowadays with the proliferation of both mechanical, electro-mechanical, and electronic 'gizmos' of all types, in homes, automobiles, etc. Although, I would think that with so many imported, cost would not be that great since perhaps, in some/most cases, metric equivalents already exist. Perhaps they wouldn't sell as well to the people in the good 'ol USofA???
Well, this is my...
0.0167567 EUR (which = $0.02, or 2cents)
...on the matter.
[note: if this subject expands with replies, perhaps we should take it to the 'Chaff' thread where it would more properly belong.]