It's because you're a nice guy with a conscience, Elbert! I've always taken the long term view - what goes around comes around, both good and bad. If I know what will best suit someone I'll tell them about it, even if it costs me the business. A happy customer is the best advertisement for San Pedro, even if not directly for me.
I remember going into an electronics shop in London once with a vague idea of what I wanted to buy, but no clear idea of facilities available and models on the market. The owner of the shop (not just a paid assistant) took time to explain the various ins and outs to me, using various models he had for sale. He concluded by saying that there was one particular model that exactly met my requirements and I should get that one. I asked him for it and he said he didn't stock it, but a nearby shop did. So I went to the other shop and bought it. But ever after that, whenever I needed something that the first shop sold I went straight there. I do hope his business flourished.