1) Computer science as a discipline teaches us about how to write and optimize elegant code, not necessarily apply it; my experience (although I didn't formally study CS) has always been that the schooling does a great job teaching theory and some practice, but tends to lag when it comes to applying it to "grand challenges." "Bootcamps" tend to go for small-scale consumer-oriented stuff, because you can't teach how to solve grand challenges in 9-16 weeks. It just won't happen.
2) Young adults have little working experience in specific industries for long enough to really be able to identify industry "pain points." Aaron Levie and others have argued this is why so many gravitate towards companies like "Yo" or Snapchat as opposed to addressing real-world problems.
3) Sales cycle. I've been a part of a health-tech startup before. The sales cycle is stressful. You spend months with one potential customer and might get nowhere. In consumer, it's a shotgun approach and you just go for as many in your target market as you can. You take no prisoners. When going after grand challenges, the amount of patience required generally doesn't seem to satisfy many investors who look at your burn rate (or the relative success of SnapChat over 18 months) and use those as their metrics.
4) Direct touch to consumer. This is the most "out there" of my points, but I'd argue that consumer-facing companies garner traction sooner because they also can appeal to the masses. The average person has heard of SnapChat. Can you say the same about Palantir (despite a successful track record)? How about Climate Corporation, which did data analytics for agriculture and sold for $1 billion to Monsanto)? These companies target enterprise. They don't have CEOs that are revered like Steve Jobs for inventing products that are "nice to have," not "need to have."
Tom Siebel from Siebel Systems came and spoke several years ago at my school (I went to the University of Illinois, where he was an alum). He talked about why he doesn't invest anymore in tech for the sake of technology. Instead, he postulates that the industry can and should be going after grand challenges in healthcare, water, energy, and food, arguably the most critical problems of the 21st century.
I've been working as the "business-oriented guy" on a startup concept for the last several months in data analytics for healthcare. I've found a niche within a healthcare subset that is lacking, and the competition is nascent at best. I was fortunate enough to spend a great deal of my time in health-tech during college and grad school, so I was able to actually go in and talk with industry leaders and get a grasp on how "bad" things were. I just finished venting about some similar frustrations on HN from the standpoint of expanding our team. If you're looking for a concept and business model that has 1) been vetted by prospective customers, and 2) actually addresses a real need in healthcare and isn't just an app, let me know. I'd love to talk more about it. I'm trying to find people to join me that want to do more for society than build disappearing messages.