The wind will never stop blowing, the sun will always shine (at least for the foreseeable future) and biogas can always be derived from the seemingly unlimited biomass. Shortage of renewable resources is literally impossible and for that reason, mankind can maintain more or less the same quality of life, without wasting reserves. In addition, the usage of renewable resources at the expense of conventional ones is an environmentally friendly alternative to the burning of oil and coal.
Facilities to exploit and distribute renewable resources can create a brand new industry, creating new jobs and stimulating local energy production. The economy will be stimulated, without the cost of energy imports and waste of resources. In addition, renewable resources can help an economy become independent, as it does not have to rely on imports to cover its energy needs. For example, the two major energy crises of the last century (1973, 1979) could have been avoided if dependence on oil had not been high.
The cost and financial risk for setting up efficient windmills or biogas plants is high, as current demand for renewable energy in the market in not big enough. It also makes such resources a hard-to-find commodity, even for consumers willing to "go green." Furthermore, renewable resources can be harmless to the environment, but the facilities to exploit them are not. For example, to produce hydroelectricity we need dams, which can have a serious effect in the local wildlife.
With the reserves of crude oil, coal and natural gas still considerably high, conventional resources are cheaper than renewable ones. They are also the most easy-to-use resources, as well as the most efficient; all alternatives to gas in transportation for example either last shorter or have considerably worse results. Little competition also means that they are easy for consumers to replenish, as opposed to renewable resources, for which you must find specialized service providers.