There are a few primary reasons why Shopify is not designed for SEO:
1) Shopify's coding structure is not ideal for SEO. For example, Shopify uses JavaScript for its core functionality, which can make it difficult for Google to index a Shopify site.
2) Shopify does not allow for full control over site URLs. This can make it difficult to create keyword-rich URLs that can help with your site's search engine ranking.
3) Shopify does not offer some of the advanced SEO features that are available on other platforms, such as the ability to edit the HTML code of your site or to easily create 301 redirects.
Overall, while Shopify is a great platform for creating an online store, it is not ideal for those who are looking to optimize their site for SEO purposes.