Give and you shall receive
When you give somebody something they feel compelled to reciprocate. Therefore they are more likely to do business with you. L.J. Market Research did a study that found 52% of participants given a promotional item, ultimately did business with that company.
Many promotional products are items one uses daily or weekly. This repeat exposure to the brand will dramatically increase top-of-mind awareness. The more you see a brand, the more you think of a brand. According to PPAI 73% of those who used the promotional product that they had received stated that they used it at least once a week.