The search form in the theme header uses the standard search and will search posts and pages, but when you have WooCommerce activated, the search form will only search products. That is the correct behavior.
If you have an ecommerce shop it is not a good idea to have the search searching through everything, it is better to only search products. It would be confusing for your customers to see search results for posts and pages mixed in with products, and would negatively affect your sales.
If you absolutely want to search everything, you could disable the search form on the header, and then add the standard search widget to the “Top Bar” widget area.