I think the motivations to produce ammonia instead of hydrocarbons are:
For one, energy efficiency. For hydrocarbons you need carbon. Either you take carbon from existing renewable hydrocarbon waste streams (biomass) or you pull CO2 from the air. The first doesn't make much sense because those hydrocarbons would better be used to produce chemicals. The second (direct air capture DAC of CO2) is - as everyone knows - hugely energy intensive, because CO2 comes in concentration of 420 ppm.
Yes, I know the Haber-Bosch process to produce ammonia is hugely energy intensive as well.
But if you regard ammonia synthesis as well as synfuel synthesis as fundamentally the same processes - both reduce elements in their oxidized forms (C as in CO2, H as in H20, N as in N2) to store energy in them - you need one extra heavily energy intensive step to get synthetic hydrocarbons compared to the sythesis of ammonia: pulling CO2 from the air where it's got a really low concentration (420 ppm).
Compare that to nitrogen which is the main component of our atmosphere (780,000 ppm) and thus much less energy intensive to isolate.
So neither source of carbon to produce CxHy makes sense in the long term IMO.
Also, as soon as you use/burn the synthesized hydrocarbons, the carbon ends up back in the atmosphere (at least in mobile applications where you can hardly capture it) which goes against the main goal of putting less CO2 in there.
Ammonia on the other hand requires nitrogen which is abundant in the atmosphere and thus relatively easy to get (compared to the carbon from DAC). The hydrogen that's needed is also readily available in many places, in the worst case from sea water.
As the goal is a reduction of the amount of CO2 emissions, in the really long-term, hydrocarbons will probably just be the less efficient option compared to ammonia.
And since all existing infrastructure does get exchanged/altered in the long-term anyway, slowly switching to ammonia won't mean wasting this infrastructure.