This is how core Magento handles JS and isn't necessarily related to any custom theme you have, even the core theme loads around 150 JS files on the homepage. As Magento 2 is using Require JS most the scripts that are loading should be required on that page already, it's just there is a looot of JS required for each page.
If you take the first lot in this screenshot:
- require.js - This is required on every page
- mixins.js - This is required on every page
- requirejs-config.js - This is required on every page
- jquery.mobile.custom.js - This is required on every page
- dataPost.js - This is required on every page
You can see where I'm going, almost every file here is required on almost every page. So removing any of this will likely cause problems somewhere, meaning to remove them you'll need to create a custom theme and manually remove them on a case by case basis. Far too much for a Stack Exchange post.