There are a number of reasons why there may be a lack of open source stylesheets or themes for Shopify. First, Shopify is a relatively new platform, and as such, there may simply be fewer open source options available compared to other, more established eCommerce platforms. Additionally, Shopify is a proprietary platform, which means that developers may not be able to create open source stylesheets or themes that are compatible with Shopify's codebase. Finally, Shopify is a closed platform, meaning that only authorized developers can create themes and stylesheets for the platform. Therefore, if you're looking for open source options for Shopify, you may need to search harder or look for alternatives.