[noedig]

This is exactly the reason. Academia is a business just like any other. Academics do what they are incentivized to do. I guarantee that if NSF, DOE, NIH and the other US government funding agencies made publishing your code a requirement for funding, and actually checked that you did, you would see everyone start doing it immediately. Right now NSF requires a "data management plan" as part of the proposal, which includes information about sharing, reusing and archiving data and code, but nobody ever checks that you followed the plan after the money is awarded.