This is naturally important for ecommerce websites but also for any business site where you want visitors to perform certain tasks. (entrepreneur.com)
Actually... to prove this point... lets take one of the highest converting and best performing ecommerce websites in the world (probably the most). (biggerpockets.com)
Website owners of ecommerce websites should be prepared to do a lot more work, since the margin they can spend on advertising may vary for each product category or separate products. (link-assistant.com)