In the last few years, they have started appearing everywhere – those people holding the signs alongside the road that advertise just about everything (pizza deals, cell phone services, closeout sales, CNA certifications, tax services, etc., etc.). So, why are they out there? What purpose do they serve? Why not just use a regular sign or advertise some other way? The reasons are multifold (including financial ones), but consider just these few.
People are out there because (1) it gives it a personal touch, (2) it connects the product with a real person, (3) a real person calls more attention than just a plain sign, (4) the person can have a particular influence on people who know him, (5) without the person holding that sign it is possible that some passersby may not even know such an opportunity existed, etc., etc.
Take this and apply it to the gospel. Why does God want people (us!) holding the gospel out for everyone to learn and obey? Go back and read those five reasons. They fit here, too!