Screenplay software is not always necessary for people who are learning the craft. There are templates out there for Microsoft Word which are set-up to be in the proper format for each element. The style sheets are automated so that they go from one element to another (i.e. when you hit enter after a Scene Heading, it automatically goes to an action line format). You can automate them further by customizing keyboard commands.
You only NEED screenwriting software if you are doing a writer-for-hire gig or revising a script that you've optioned or sold and the producer requires it. Even when you submit specs to agents or producers you are normally submitting hard copies or RTF or PDF files. Screenwriting software is a luxury, not a necessity - and by far not the best use of your screenwriting dollars.
Many would be far better off putting the money they spend on software toward a seminar or workshop so that they can learn the craft.
Proper formatting is important - but not nearly important as proper structure, character development, dialogue, etc.
