We are talking about 2 different things here.
A realtor, giving a gift of a massage to a client as a housewarming/thank you, may only deduct $25 of the value. Agents make thousands of dollars on the sale of a home, the tax deduction is immaterial to them. Any agent looking to get repeat business would gladly invest $100 in a relationship with their client. Besides, at 33% tax rate deduction shield, they are only giving up $25 of tax dedutibility. Peanuts compared to their commission.
Real Estate licensing regulations vary from state to state, and they may limit the value of gifts given.
But gifts can also be for referrals, which many not be covered by licensing regulations. We sent our best friends to our agent, who made several thousand selling them a home. He gave us dinner for two at our favorite restaurant.