Creating synthetic fuel requires a lot of resources. Growing it has a massive environmental impact and the necessary farm area would be very large. Solar cells would require a fraction of the area and can be put onto roofs or into areas not suitable for farming. Synthetic fuels also don't fix the efficiency problems of combustion engines. So electric cars would require only a fraction of the effort to be powered compared to combustion engine cars with synthetic fuels. On top of this, synthetic fuels do not solve the exhaust problems.