Algolia Shopify plugin has a feature to enhance collection pages by adding InstantSearch widgets.
This documentation details this Collection Search Page feature further.
However we don't initialise InstantSearch on the "all" collection page on the frontend by default. We do index it though.
This behaviour can be changed by updating the regular expression in the `algolia_init.js.liquid` file included in the assets of your Algolia-enabled Shopify theme.
Specifically, you can change the regular expression in the line like the following
to the following.