I think a big part is that duckdbs spatial extension doesnt have any transitive dependencies (except libc). It statically packages the standard suite of foss gis tools (including a whole database of coordinate systems) for multiple platforms (including WASM) and provides a unified SQL interface to it all.
(Disclaimer, I work on duckdb-spatial @duckdblabs)
"Accessibility" is too often dismissed, yes you CAN do things with things, but getting people to do it is a craft and art. This is often where open-ish-core differs from the enterprise version of something too
I tried out duckdb-spatial for a hobby project and my takeaway is the main thing it offers over geopandas is performance in batch processing.
If I can reduce my spatial analysis to SQL and optimize that SQL a little bit, duckdb will happily saturate my CPUs and memory to process things fast in a way that a Python script struggles to do.
Yes, the static linking is nice. It helps with the problem of reproducible environments in Python. But that's not a game changer IMO.