A fairly uncontroversial definition of science is:
Knowledge or a system of knowledge covering general truths or the operation of general laws especially as obtained and tested through scientific method
In other words, science is part of an organized, systematic and consistent body of knowledge, practiced in a consistent manner. Therefore, while individual innovators are of historical importance, you don't need to be familiar with their work to have a meaningful context for where the field is now.
On the other hand, here are a few of the definitions the same source provides for philosophy:
Pursuit of wisdom; a search for a general understanding of values and reality by chiefly speculative rather than observational means; an analysis of the grounds of and concepts expressing fundamental beliefs; the most basic beliefs, concepts, and attitudes of an individual or group.
Philosophy is much more idiosyncratic, it is less consistently systematic between one thinker and another. In fact, since most philosophers are systemic innovators, it is arguably the least consistently systematic discipline, considered as a whole (while science, arguably by definition, is the most). For that reason, and because even the closest students and disciples of a given philosopher may diverge significantly in their thinking from the source, the study of philosophy is largely the study of ideas as attached to the individuals who formulated them.