There are several facets to answering your question: Some ideas don't get traction because they are before their time, i.e. technology might not have been up t

There are several facets to answering your question: Some ideas don't get traction because they are before their time, i.e. technology might not have been up to scratch. For example some apps might be better suited to mobile than desktop. Or need current generation browser capabilities rather than those of 3-5 years ago. A good example is apps that relied on Flash or Java applets can now be implemented using HTML5 + CSS3 + ES6. Another common issue is needing more internet bandwidth or lower latency than was available at the time. There still are many areas where internet speeds are far lower than those in major cities or suffer slowdowns when congestion increases, e.g. evenings. Then some ideas didn't get off the ground because the market wasn't / isn't there. Those ideas might still be a very bad bet. And ... considering your bootstrapping ideas, many ideas just don't scale to 100's of millions, but can result in a 100's of thousands or even a couple of lazy millions. Markets of that size simple do not appeal to VCs.