The door bell rings and the owner approaches the door and sees a male figure standing outside. He is wearing a TShirt without any business name or identification. The owner of the house is uneasy, unsure who that person might be and what he might want.
Contrast that with the situation where the person ringing the door bell has a shirt with Tom's Landscaping embroidered or screened clearly on the front. He has a hat with the same matching logo. The owner immediately recognizes the business name and realizes why he is there. Is there a difference in how that representative of the business is received by the prospective customer, the owner of the house? You bet.
Are sales lost because the roofer or the contractor or the A/C guy looks suspicious and uninviting? Does the shirt or hat with the business logo add professionalism and credibility? Yes it does. Identifying the business on what is worn is so important to a mutually successful business relationship because the first impression is the most important one.
Also, think about how the embroidered or screened logo or business name is always advertising the business, whether the employee is walking in the neighborhood or standing in line at the grocery store. The business name is seen by all who see the employee. It's the greatest way for employees to advertise the business to those people who are prospective customers every day of the week.