Professional modeling photographs make a model appear profession, credible, and responsible. Appearance is everything in modeling and acting. The same goes for clients.
First impressions count a lot.
Your portfolio is YOUR first impression. From those photos, clients guage how much experience you have, how much you're worth, and if you can handle the job. Welcome to the real world. However, any type of profession you want to get into takes money, time, and training. Clients feel the same way about models.