Then we can use our built-in spatial reasoning to compare how big some areas are by changing the perspective (as in real life), and shapes are only distorted by perspective which is very familiar.
Also, many organizations, especially governments and news media, often have their own requirements and conventions when publishing maps — some practical, some purely stylistic. For example, NY Times uses Albers USA for election maps (it has that iconic curved look of state boundaries), and National Geographic uses Winkel Tripel for their world maps.
The maps were usually reprojected in variable UTM (according to your TZ - on the one I was working with) and/or using a Gauss projection, which is an extremely good compromise for whole countries. Because it was dynamic, the reprojection was a continuum while panning, usually imperceptible for the user at country scale. You could rotate the map, as well as query for road names in any spot instead of hunting down the (often missing) labels.
I feel like the online services regressed quite a bit compared to that time, but maybe that's just me as I was working on the field. The mercator projection was mostly a fallback for worldwide maps, hardly used otherwise at smaller scales. When google maps started to provide worldwide free maps (which could be used as a 3rd-party service for free at the time), there was no way we could compete. OSM wasn't good enough yet, data licensing from international vendors was extremely high, and worldwide satellite imagery required an entire order of magnitude higher investment to compete. The companies I knew all pivoted to fleet management and similar services to survive.
The transverse Mercator projection is an “extremely good” conformal projection for anything region located within a narrow band around a specified meridian. This describes some countries well (e.g. Chile, Finland, Vietnam, Portugal), but is rather terrible for anything stretched out East–West (e.g. Russia, Canada, Indonesia).
Among conformal projections, for a compactly shaped country the stereographic projection is better. For a country lying along a parallel, a conformal conic projection is better. For a skinny country oriented at an arbitrary angle, an oblique Mercator projection is better. For small enough countries, any conformal projection works fine with low distortion.
This allows to have of a country like Germany in view with very little distortion. As the zoom progressed outwards, it would morph to mercator. Nobody really noticed (sadly), and the choice of falling back to mercator was also due to it's popularity making it sort of "expected" more than anything else.
The key point is that the reprojection was dynamic, and done on the client, optimized for the current viewing conditions. Stuff that today you can perform via JS without any problem if you forego the idea that maps need to be pre-rendered.
If your display is tall and skinny and north always points upward, transverse Mercator is a good general choice among conformal projections. If your display is square or squat, then a stereographic or conformal conic projection is less distorted for any particular view.
> The maps were usually reprojected in variable UTM (according to your TZ - on the one I was working with) and/or using a Gauss projection, which is an extremely good compromise for whole countries. Because it was dynamic, the reprojection was a continuum while panning, usually imperceptible for the user at country scale. You could rotate the map, as well as query for road names in any spot instead of hunting down the (often missing) labels.
I'd be interested if you could remember any names because I don't remember anyone doing a good job with vector maps in 2005 when the google maps api came out (embedded google maps were long established by 2010). Performance would have been pretty atrocious even in Flash, especially if they were from any established GIS companies, where incredibly slow desktop software was already the accepted norm.
Maybe a very generous interpretation of continuous reprojection, but I'm not aware of any decent system like you describe until the early 2010s (like the one the article links to[1]) and even then there's no real products built around them, until now :)
[1] http://berniejenny.info/pdf/2012_Jenny_AdaptiveCompositeMapP...