The whole point of Scrapyard Knives is a good knive at a great price. In order to keep the prices low Dan must limit the options he provides his customers. The more options available the more the price.

If Dan were to give us options like Busse does then Dan in essence would be competing against his brother. Setting up scrapyard knives like he did allows Dan to gain some of the reputation of Busse and Swamprat yet remain independent and not compete directly against them.