1. The system sucks, is a scam and causes people to lose money despite them following instructions to the letter.
2. The system or mentor coaching has been tested and proven but people do not give themselves enough time to go through and do what is necessary to succeed before jumping and buying another system.
While it is true there is no such thing as a push button make millions software, people who are over-skeptical and see every offer as a scam will also NOT succeed.
It's like gardening where you need to test the soil (keyword research), plant the seeds (build blogs or sites) and water them (driving traffic like article marketing, classified advertising, email marketing, forum posting, social media and video submission) everyday for them to grow into fruit trees. (make money)
But most people want fruits or money before they even start learning how to plant trees or build sites and drive traffic.
If that is you, why do you want to be in internet marketing in the first place?