Several types of gaps occur between the two. Two main reasons of the differences are sizes of funding and the (profit / non-profit) focus. But there is another "gap" which is often forgotten - the gap of freedom. If you work for a university with "petroleum" in the name, you may have more freedom of choosing topics than if you worked in a company with this word in its name, but still it can influence what you focus on. In the academia, you have (at least should have in theory) freedom to choose your topics. So if the industry develops an app to lure a user to purchase some products, I can develop an algorithm which warns this user that his/her cognitive errors might be exploited and I won't be fired for that. My data is billion times smaller than Google's but I don't need to care about revenues from ads. I can work on AI safety for everybody not one company or a government. Although this doesn't lead to higher income, for me it's a very (morally) valuable gap.

Depending on the field the answer could vary but I can answer the question from a computer scientist perspective working in data science and recommendation systems. 

The main reason for having a gap between industry and academia is the goal each of these two have. By that, I mean people in academia are interested in having publications (even if they deny it) and people in the industry are more interested in solving their own problems in that particular domain.  So, because people in academia have high interest in more publications, working on the problems that industry is facing is somehow not reasonable for many researchers in academia as doing experiments for those problems are very hard if not impossible. The reason is, many problems need a large number of users to be experimented on and for that, you need a live system. People in academia do not have that ability and therefore they focus more on problems that do not need an online evaluation of their algorithms.

Dear Anirbid,

Your question -- What is the reason fort the huge gap between industry and academia? -- is a timely question. There is indeed a huge gap between industry and academia, even though this gap depends on the type of university you are and also the country wherein you live.

As see it, this gap is mainly due to the fact that generally academia and industry have different goals. Academia's research is generally interested in basic research and  looking for the unknown. In contradisction. industry looks mainly for money and applied research. I think that the more a country is developed the more it supports basic research. To my understanding university should have freedom to investigate what they want, not what industry wants. It would be a sad reality that universities were dependent upon industry's interests. Note that the history of science shows us that it is basic research that in the long run turns out to be more effective in terms of practical implications.

I hope I has gor ypur question ana thart this helps,

Best regards,

Orlando