Why do we use non-renewable energy?

In modern life there is a large demand for energy as it is needed for everything from transport to heating. Whilst there are many renewable options for energy many of these run into issues in terms of their reliability, for example wind turbines can only generate energy when there is a strong air movement and solar panels are much less effect in countries with less sunlight. With these setbacks and others beyond the current sylabus scope the world turns to the reliability of the fossil fuel industry for the time being.