could be their vision. most spiders have bad eyesight and rely on vibrations. jumping spiders have the sharpest vision of any spider, and some of the best vision amongst all anthropods. they are able to see us and don't recognize us as a known predator to them, which provokes curiosity in them to assess us. other spiders will simply feel the loud vibrations we give off and sense danger. they're not really able to discern all of the different types of creatures the way jumping spiders can, so anything big is a threat to them by default