State funding has been falling dramatically. The actual researchers
are hurting for money. Grad students are paid a pittance, so rather understandably, most grad students want to graduate ASAP. Making your code nice and publishing it does not help you graduate early. It also does not help you get grants or funding.
You could pressure universities / departments to make reproducibility a requirement for graduation, but I don't see why they would follow along, because this is not going to help the university get more funding or publish more papers (prestige).
Now, if organizations and companies were willing to put money behind software reproducibility (maybe some sort of fellowships or million-dollar research grants to labs), then the incentives would be aligned.