According to the above chart recently released in a report by Electronic Entertainment Design and Research (EEDAR), 49% of HD console owners have not purchased DLC in the last 12 months for a litany of reasons.
While EEDAR estimates that DLC will generate $1 billion in revenue in the US in 2012, it cites that privacy concerns are a major deterrent for prospective DLC customers, though much of this can be remedied by purchasing points instead of leaving credit card information on their console:
Online security is currently a hot topic as many major video game companies and services, including the PlayStation Network (PSN), have been the target of recent security breaches. However, EEDAR’s survey data does not suggest that the PSN incident had a major impact on consumer privacy concerns.
Of course, the other problem is that DLC cannot be returned and it can be too pricey. Also having no demos or reviews for a title is detrimental for its sales.
[Source]