It appears that an Opportunity has to open a quote in order to attach a product to an opportunity.

Is there a way to directly attach a product to an opportunity?

If not, could someone explain the reasoning?

In the simplified world I live in, a sales person creates an opportunity and selects a product to attach (drop down list with pricing). the product price would fill in the opportunity amount which is shown in the Opportunity List View (which could then be overwritten if they so chose).