This article doesn't touch on the actual reasons why Mercator is still in widespread use:
* It was the first widespread projection because of its practical use for nautical navigation (where it is still the best projection available), so it was easy for map makers to sell for non-nautical uses, even after "better" projections became available. And inertia is a hard thing to overcome for something considered somewhat inconsequential.
* Mercator and its cousin Web Mercator are extremely simple and fast to calculate relative to other projections. Compare the formula for Web Mercator (https://en.wikipedia.org/wiki/Web_Mercator_projection#Formul...) to Equal Earth, an excellent compromise projection for general use (https://en.wikipedia.org/wiki/Equal_Earth_projection#Formula...). Web Mercator is very easy to generate and serve tiled maps out of, Equal Earth and the like require somewhat non-trivial engineering to make serving those maps at scale to users in a web browser economical and quick.
* Preserving angles is legitimately important still for large scale (very zoomed in) road maps. Projections which preserve size can cause things like 90 degree road intersections to render at very strange angles which confuses drivers. Mercator and Web Mercator are therefore excellent choices of projection for local road navigation, which is by far the most common use of maps today for most people.
I strongly recommend folks interested in map projections to read this from Mapbox: https://www.mapbox.com/blog/adaptive-projections. Google Maps now has similar features, but both companies relied on Mercator for many years with good reasons before technology caught up and better solutions became available.
No map shown to a driver at the detail level of navigating intersections should have to care about projections much. At that small a scale earth is approximately flat, and any half decent projection should have minimal distortions of any kind.
You can read about why projections still very much matter for large scale (which is what I think you meant; small scale would be something that shows you whole countries and not used for road navigation) maps in the article I linked. Google Maps tried out an alternative projection back when it was still Keyhole and ran into problems with angular distortion when zoomed in. The original post is sadly lost to Google shutting down their product forums, but here's a quote from a Google Maps engineer on their use of Mercator and why it matters:
The first launch of Maps actually did not use Mercator, and streets in high latitude places like Stockholm did not meet at right angles on the map the way they do in reality. While [Mercator] distorts a “zoomed-out view” of the map, it allows close-ups (street level) to appear more like reality. The majority of our users are looking down at the street level for businesses, directions, etc… so we’re sticking with this projection for now.
In the 90s, my family (inveterate roadtrippers) always kept a Rand McNally road atlas in the car. Each page had a map covering (usually) a whole state. I don’t know what projection it used—Albers, perhaps?—but I remember as a child wondering why some straight‐looking state borders were actually subtly curved.
Navigation concerns these days may include getting as fast as possbile(i.e traveling on the geodesic), avoiding bad weather areas(forecasts), using the least fuel as possible etc..
Stereographic projection(of the half sphere where the origin and destination lies on) solves the geodesic issue, and it's different from the Meractor
* It was the first widespread projection because of its practical use for nautical navigation (where it is still the best projection available), so it was easy for map makers to sell for non-nautical uses, even after "better" projections became available. And inertia is a hard thing to overcome for something considered somewhat inconsequential.
* Mercator and its cousin Web Mercator are extremely simple and fast to calculate relative to other projections. Compare the formula for Web Mercator (https://en.wikipedia.org/wiki/Web_Mercator_projection#Formul...) to Equal Earth, an excellent compromise projection for general use (https://en.wikipedia.org/wiki/Equal_Earth_projection#Formula...). Web Mercator is very easy to generate and serve tiled maps out of, Equal Earth and the like require somewhat non-trivial engineering to make serving those maps at scale to users in a web browser economical and quick.
* Preserving angles is legitimately important still for large scale (very zoomed in) road maps. Projections which preserve size can cause things like 90 degree road intersections to render at very strange angles which confuses drivers. Mercator and Web Mercator are therefore excellent choices of projection for local road navigation, which is by far the most common use of maps today for most people.
I strongly recommend folks interested in map projections to read this from Mapbox: https://www.mapbox.com/blog/adaptive-projections. Google Maps now has similar features, but both companies relied on Mercator for many years with good reasons before technology caught up and better solutions became available.