Oil dependency contributes to many problems:
- Air pollution
- dependence on foreign powers which may not always be friendly
- economic dependence on stable oil prices
- Peak oil - although the actual date when oil will become prohibitively expensive is subject to strong debate, it will come eventually.
- Loss of reserves. It makes sense to conserve petrochemicals for specific applications which are not easily replaced by alternatives, and for emergency reserves in case of global disaster (e.g. large-scale volcanic eruptions) which could affect renewable energy production for months or years.