Blackman Plumbing Supply

I have been a showroom salesman at Blackman for 5 years working now 3 days per week in Bohemia and Rocky Point. I always approach customers as they arrive and greet them, sometimes they immediately say "just looking" then later when they want help we're all busy with other customers. So many customers tell me how helpful I have been but I rarely see them post it. When all salespeople are busy, we will sometimes break away and ask a waiting customer to make a future appointment. Why does that upset them ?