[Boudica]

To be truthful, I only started reading manga when I ran out of episodes of a certain show and wanted more/to find out what happened next. I also held a very similar opinion to yourself. However, the more I read, the more it made sense.

It's' a different pace and way to take in storytelling. Also, some manga art can be more dramatic and detailed than the quicker drawings composing scenes in animated shows. Some of the real draw can be artwork. However, I think all this truly depends on WHICH manga.

Although, I've mostly moved onto webtoons, marvel comics and some indie comics. Some anime follows typical "patterns" and predictable rises and falls in tensions, whereas manga sometimes seems to have the freedom to be more creative (as there's different time constraints (compared to a 24 minute episode).

Best way to truly understand, is find a manga that exceeds the storyline of a show you like. See if you get hooked on it, especially if you know the show has no more planned seasons.