The number 1 and 2 reasons are closely related.
1. Ease of reading ABOUT making money. (LAZINESS; lack of focused motivation)
2. Information overload ("I could do THIS... NO THIS!... WHAT ABOUT THAT?!?"
3. Technical computing task complexities (Even basic wordpress setup can be difficult for someone who's primarily just held low-skill jobs while playing sports and racing cars in their spare time. And that is a drop in the bucket compared to raw html coding or many of the effective black hat techniques)
4. The tediousness of various tasks. (Writing article after article, blog comment after blog comment, yahoo answer after yahoo answer, autoresponder e-mails, rewriting PLR, or attempting to write free reports or e-books on inane subjects that happen to have monetization potential, etc. can all be boring as fawk. This is all WORK, for a lot of people. LAZY and UNMOTIVATED individuals don't work with enough focus for long enough periods of time to realize their desired results (which really touches on how much they ACTUALLY DESIRE those results).
5. Dynamic complexity of the entire animal (Adsense used to pay A LOT MORE than it does now. People used to make a killing direct linking through Google Adwords to CPA offers. No longer allowed. Even Bing ads RECENTLY stopped allowing direct linking to e-mail/zip submit offers. Bum article marketing used to be much more profitable prior to the Panda algorithm changes. SEO assumptions have to be re-evaluated. CPA networks invoke new traffic restrictions everytime you turn around. Competition driving CPC's up. Effective methods get saturated, then another method is devised only to be saturated soon afterwards).
Two significant elements related to success in this game are INDIVIDUAL DRIVE and LUCK. Only one of those do we have any direct control over. To the extent that it comes down to our individual sphere of control, we can be determined to succeed by being determined to be focused, resilient and flexible.
We need to be focused on learning what we need to learn with the ability to apply what we learned within different contexts and under different conditions. We need to stay focused on a method that we have reason to believe can bring some success -- even when it involves tedious tasks. We need to remain focused on a method that we have reason to believe could lead to success for long enough to test, tweak, twist, and explore it from different angles before deciding it's not worthwhile.
We need to be resilient when we don't immediately see the results we'd hoped for from an investment of our time, efforts and money.
And we need resilience and flexibility to adapt in response to game rule changes that are out of our control such as laws (taxes related to Amazon), restrictions (no more direct linking or various traffic sources allowed), or previously effective methods/niches becoming overly competitive.
