Moreover, he never wrote down the "law" that is now attributed to him---a marketing coup.
https://en.wikipedia.org/wiki/Stigler's_law_of_eponymy strikes again.
https://en.wikipedia.org/wiki/Stigler's_law_of_eponymy strikes again.
The other reason is that eponymy is often a symptom of laziness. Rather than finding a good, descriptive name for something, you end up with an eponym that is not at all evocative of the meaning behind it. For example, and without putting too much thought into it, Amdahl's law could have been called something like law of scaling or law of bottlenecks.
The tongue-in-cheek flip side of this coin is that, when discovering something, one should give it a descriptive but complex name. That way, people are more likely to refer to it by the names of the discoverers than by the clumsy descriptive title the discoverers chose. :)