Why not? Science and mathematics are communal efforts, every discovery typically has multiple precursors ("standing on the shoulders of giants"), and "the discoverer" is often not the one from whom subsequent scholars and/or the public learn about it because they did not explain or publicize it well enough. "Stigler's law" is an example of the latter. Sometimes it is due to historical obscurity of the "original discovery", as with "Pythagorean" theorem or "Heron's" formula, sometimes due to countries or schools promoting "their" discoverer even if he/she was not the first, etc.
The naming, upon which recognizable reference depends, has to deal with pragmatic constraints of cultural change. Although renaming efforts are undertaken to correct some blatant misnomers they typically take a long time to take hold and are not a practical priority (US and UK still use feet and pounds for the same reason). And more generally, historical significance of "original discoverers" is overrated in the popular literature (as can be seen anecdotally from the number of "who was first" questions on our SE), which contributes to the "great leaps by great minds" misconceptions about history. Here is Renn's From the History of Science to the History of Knowledge – and Back:
"The history of knowledge has traditionally been studied from a restricted perspective that favors innovation over implementation, transmission and transformation. In the past, historians of science and technology have often focused on the question of who was the first to discover a fact that later became a key innovation and when this took place. Much less attention has been paid to the question of what role these discoveries or inventions played in the contemporary context of knowledge and how they changed their meaning when transmitted to a different context."