Other than its application, can we say the reason of common adoption of WGS84 is due to its accuracy?
In addition to Devdatta's answer - that its valid all over the world - there are some other considerations about WGS84:
- Its the "native format" for GPS.
- Its defined in a way that terrain can move underneath it for such things as tectonic movement measurements (of course, that is a disadvantage too, if you were hoping that your terrain does not move over time).
- We've all already agreed to use it for many things (e.g. for ICAO air charts, and as a transform-to-and-from common format). That is related to the reasons above, but now it is a justification in-and-of itself.