[PROJ] Why is Web Marcator EPSG:3857 so popular for web maps (vs EPSG:4326)?

[Idan Miara]

Hi all,

I was wondering if you can enlighten me regarding why Web Marcator (EPSG:3857)
is so popular and used by virtually all major online map providers as
opposed to WGS84 lat/lon (EPSG:4326)?

I've composed some points that I could think about, but it doesn't add up
for why 3857 maps (i.e. slippy map) are more popular than 4326:

1. In 3857 almost all the world fits in a rectangular tile (~85 deg north
to ~85 deg south), which makes it easier to divide the tile further into
sub tiles.
In 4326 all the world fits into two rectangular tiles (so not much more
complicated, I guess).

2. Users expect coordinates in 4326 and the transformation from 3857 to
4326 is rather fast (in comparison to ellipsoidal mercator).
But if you save the coordinates in 4326 then you wouldn't need to transform
at all.

3. 3857 is "almost" conformal - I think that the normal use case is not
marine navigation so it doesn't seem so important.

4. Both 3857 and 4326 have size distortion.

5. You can't measure distances, areas or angles easier in 3857 as far as I
know.

What am I missing? Is 3857 faster or more useful in any other way than 4326?

Kind regards,
Idan
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