Use English Units

I don't know what you mean by "websites" plural. I'm talking about this website. If it's in English, one can assume a large number of its users are from Britain, America and the commonwealth, much of which uses English units either officially or has a large proportion of its population that does so. I use this site as an alternative to Google Maps, knowing how amoral that corporation is. Why does this site not respect the preferences of its userbase?

Assuming you mean openstreetmap.org, the map software is configured to show the scale in both metric and imperial. Along with the names in the Standard map being the local ones, and the website text using the user's chosen browser language, the openstreetmap.org site is designed to fit the visitor's language and preference.

@Lollard: I don't think you'll get much sympathy for your viewpoint by calling SI units "French", they are pretty much the universal measurement unit internationally, and are extensively used even in the few holdout countries using Imperial or customary measures. OSM is an international project and many of the readers of this website speak & read English as 2nd, 3rd or 4th language: please bear this in mind.

According to wikipedia, of Commonwealth countries only Canada and the UK still use Imperial officially, although the units are still widely used in some Caribbean countries. Other major Commonwealth countries have all moved to metric (India, NZ, Australia, South Africa, Pakistan etc.), as has Ireland. So both in terms of number of countries & total population metric is more popular in English-speaking nations.

If you are looking for an alternative to Google Maps as you say, maybe the main openstreetmap.org site is not the best choice as it tends to be aimed more at mappers than end users. End-user applications that use OpenStreetMap data are more likely to offer user-controllable settings. Just to give one example OsmAnd is a well-known mapping and routing app for Android, it allows the user to choose the units and even offers a choice between miles/yards or miles/feet. (It also offers a huge range of other options about what to display, highlight, or hide on the map - well beyond what is possible on openstreetmap.org).

I wasn't so much directing you to OsmAnd so much as using it as an example of a user-configurable interface, as I happen to be familiar with it myself.

Looking a bit more closely at the routers available through openstreetmap.org, it seems that one of them (GraphHopper) can also be accessed via its own website https://graphhopper.com/maps/ , where there is an option to click between miles and kilómetres in the output.