As others have said, the practical application would be to be able to produce storable fuels (and hydrocarbons for chemical industries) in a post-fossil economy and reduce atmospheric carbon. Taking the carbon from air would seem to be at the rear of the options economywise, we have other more concentrated sources of carbon atoms in biomass, waste streams, carbonate rocks, etc. , unless we really wanted to use it to scrub the atmosphere in which case we’d still need very cheap and abundant noncombustion electricity sources. It was mentioned already that you could take it more easily from the seawater instead (since anyway you’d already have a plant at the seashore for processing out hydrogen) and depend on environmental equilibrium to draw out the atmospheric CO2, if you have the time.
the issue here is not really about the generation of gasoline, it is more about storing energy from renewable sources during periods of low demand. Generating gasoline from CO2 and H2 is wasteful as around 90% of that produced is water which is formed when H2 is reacted with CO2 on the catalyst bed as a byproduct during hydrocarbon generation.
A more realistic solution to store energy is to generate methane from CO2 and H2 and pump it into the distribution grid - this project is currently in development with Audi in Germany. If a local grid isn’t present it can easily be liquified and then used as a raw material for pretty much any hydrocarbon you want.