There are lots of reasons that prevent people making money online but here are the most common ones
They think that they can become billionaires overnight: I am sure you came across one of those sites that promised you to make 33729.34 dollars/per hour (not really sure why they put .34 in the end) Making money online is a process that takes time and it wont happen overnight.
People who dont understand this fact start their online business then feel disappointed few weeks later when they bump into reality.
They think of it as a website not as a business: Making money through the internet requires that you think of your website as an internet business and not just a simple website. Why is such a mentality required? Simply because when you consider your website an internet business you will invest some time learning about marketing, selling and customer satisfaction.
They copy others: Unless you start a website about a topic that you are enthusiastic about (not necessary be an expert) you will lack the required motivation to continue. In addition, Googles search algorithm became really harsh in detecting duplicate content and banning it. And by duplicate content they dont just mean copied pages but their algorithm can detect copies paragraphs, paragraphs that were copied then modified to appear different and any content that is not original.
How to begin making money online?
The only way to develop a successful business online is to target an unmet need that people have.
Before youtube appeared people were in need of a site to upload their videos and thats why youtube succeeded.
Before Facebook was there people needed a way to connect with their old friends and thats why facebook became successful
Before Twitter was there people needed a way to update a large number of people in the same time with certain info and thats why it succeeded.
Contrary to the common belief you dont have to come up with a brilliant new idea in order to succeed online but you just need to:
1) Exploit an already existing need because no one is satisfying it.
2) Satisfy the same need in a better way. Facebook wasnt the first social media website out there but it became the most successful because it was the best.