They did. Genre authors may not need a sympathetic viewpoint character, and get by with excellent writing and narrative to fill a clued-in audience.

But when you're reaching for a mass audience who don't generally 'get SciFi you need someone the audience can identify with - he's their introduction to the odd world being shown.

Star Wars IV had Luke Skywalker - he's the everyman we identify with: a kid with hopes and dreams. Star Wars I had ... no one really we could ID with.