A layman can get confused that how ecommerce, portal and other websites are different from static website. Actually these things are slightly complicated and better to leave to the web developer. You should simply understand that it is easy to develop a website with static pages while when in come to dynamic pages then developer face challenges. If you understand HTML, CSS then you can easily create websites while dynamic websites need extra knowledge of development languages such as .NET, PHP etc. eCommerce and portal websites cannot be developed without knowledge of development languages.
Nowadays ecommerce website development has turned quite easy with development of some platform like WooCommerce, BigCommerce, WIX, Shopfy etc. It should be noted that static website can have home, about us, services, contact us, FAQ pages while an ecommerce or portal can have hundreds of pages. Over the years, many new technologies have come which have been immensely popular and acceptable for static as well as ecommerce websites. Suppose if you want to have a static website then there is no need to hire any high cost developer because they would be doing almost nothing.
Now it is clear for you, what difference between static is and ecommerce website development. You will never find any company working especially for static website because that is not a big deal while many are specialized in ecommerce and portal.