There is great significance in the availability of so many varieties of map projections. One may very aptly illustrate a point or series of points or data collection by choosing the projection that most strongly or clearly references such points or data. The disadvantages of so many options for projections lie in what and how much each distorts from the real world, and in how we must make our best educated decision as to our choice of projection.
We know that a mercator projection, for example, is perfectly accurate around the equator and no where else, but it became highly useful for nautical purposes because of how it represents lines of constant course. A stereographic projection proves almost exclusively valuable in planetary mapping for crater mapping.
Equal area projections sacrifice accuracy of shape and of angles but are more accurate of the proportions of that area. The Mollweide projection is a good example of this. The Bonne projection focuses on the area accuracy mostly around the central meridian and the standard latitude where the shapes are not distorted.
Equidistant projections preserve distance from a standard point or line.
The plate care projection introduces such distortions that it is not suited for navigation, for example. Polar projections are useful applications of an azymuthal equidistant projection.
The risk in choosing a highly customized projection is that while it may enhance our view of a certain point, it can highly weaken the perspective on another, giving a false sense of reality in general. We must choose the one that best illustrates our point but which also introduces less distortion on other points.
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