Imagine being a store owner who sells machines without knowing exactly what they do. Some of your products could help farmers grow more nutritious crops while a few others could spread disease among thousands of people. Part of your inventory would do nothing at all.
This is the quandary facing many biotech companies that specialize in synthesizing or printing DNA. By selling genes, they have empowered synthetic biologists seeking to genetically engineer organisms capable of fighting disease or producing industrial materials.