I didn't say "this game" -- and besides it's rather self evident. Achievements are a sad waste of HTC's efforts and lower the quality of the game ever-so-slightly simply by existing.
Is it possible achievements serve a purpose?
To give new players a sense of accomplishment in what likely has the hardest learning curve of anything they have ever played? To make progress more measurable?
To encourage learning, understanding and enthusiasm for history?
To give measurable results to try new things?
For some whimsical fun, for others stated value in what they have accomplished?
Something new to experience for the folks that have already "seen it all."