It is almost certain to say, I think you will agree, that most people, if all other things as price, are equal, and prefer to buy a Mercedes. This decision purchase was made based on the product's benefits (reliability, comfort, prestige), rather than on features or specifications (four-cylinders, synchronized gearbox, 16-inch wheels, etc.) It's just so with a professionally written CV or Resume. Everything else being equal, do you think your future employer would prefer a Mercedes or a Hyundai? The only way we perceive no difference between the two candidates who have not seen before, especially if their qualifications and experience are similar, is to compare the appearance of their resumes. Unfortunately, this initial assessment has been completed in about 8 seconds, so that he or she needs to be sold the relevant factors in that brief interval. In the language of sales, the selector must be presented with the benefits of hiring you and not only the characteristics of their experience and qualifications. Your resume is your sales and marketing documents, your product catalog. Like all the cars are not equal, nor are two people. Without But unless the benefits to the organization of employment of you rather than the next person on the stack, are quickly and credible "buyer" then he would not even consider the characteristics.
3. I registered with an agency. They have offered to write my resume for free. Why should I pay for one? Agencies exist to provide a steady stream of traffic to the interviewers.