Selling parts and lack of manners.

O.K I have a beef. If a buyer is interested,and takes a day to pull the trigger,why on earth do guys feel the need to sell the part while your perhaps discussing this with your old lady,or scratching your whatever? Whatever happened to common courtesy,and telling the buyer you have another interested party,so sh#t or get off the toilet ? Honestly it's just plain arrogant to not give a sh*t...