Ask HN: Why are journal articles only available for 24 hours?

I've seen journal articles (for example http://www.ehbonline.org/article/S1090-5138(14)00024-5/fulltext) that cost like $30 and give you a DRM-free PDF but only 24 hours of online access. What's the business case for only 24 hours of access? Do they think I'm going to lose the article and download it again? I doubt it's because they're paying through the nose for bandwidth.