A few reasons. Learning is one of them, since I don't normally deal much with browser and web related technologies, so it's a good way to learn more about them.

I also think there are a few interesting things you can explore that go beyond a simple carbon copy of what's on the Internet. Ideas that I've implemented are things like automatic extraction of audio tracks, transcription, and summarization, loading a page or podcast transcript into the context window of a LLM to discuss the arguments or factuality of the claims being made, automatically turning articles to reader view using readability/trafilatura, etc.

Directions I'd like to explore would be things like multimodal search ("that page I read six months ago about computer security with neon green text on a black background", or give me a list of fitness related pages I've read in the last twelve months), personal statistics (how is the mix of topics I've been reading about changing over time), annotating pages instead of just passively reading them, maybe even P2P archiving or discussions about pages, and all kinds of other things.

But installing archivebox would be easier indeed.