Final answer:
Apollo's name remained the same in Roman mythology because not all Greek gods had their names changed by the Romans; some gods, including Apollo, were so culturally integral that their names were kept. This reflects the broader Roman appreciation and assimilation of Greek culture.
Step-by-step explanation:
Apollo does not have a separate Roman name because the Romans often adopted Greek gods exactly as they were, including their names. In the Roman pantheon, several Greek gods were given Roman names and attributes, such as Zeus being renamed Jupiter, and Aphrodite becoming Venus. However, not all gods experienced a name change. Apollo was one deity whose name and attributes were so narratively and culturally integrated that the Romans chose to keep the Greek name as is. This reflects a broader cultural assimilation where Romans often embraced Greek culture wholeheartedly, and in many cases, Greek practices and names became fashionable and were adopted by the Romans, even in other fields like medicine where professionals would use Greek names.
Beyond Roman and Greek mythology, celestial bodies like planets and moons continue to be named after mythological figures, with recent additions pulling from a wider variety of mythologies as more celestial bodies are discovered.