I'm looking at the fuel values since "solarite ore", "solarite bar" and "solarite fuel cell" are all burned exclusively in the new "solarite generator".
ore - 12,4GJ/stack, 62GJ/rocket
bar - 32GJ/stack, 16,1GJ/rocket
fuel cell - 22GJ/stack, 11GJ/rocket
It just seems straight up worse than the other two options, while also being the hardest to produce, requiring separate research, and requiring disposal of the burned out fuel cells.

The only advantage I can think of is if you were to move them using logistic bots it's less item count. But the generator doesn't have placement restrictions and doesn't need any other resource, so there's no reason to place it far away from where the fuel is produced.

Originally, the idea behind solarite fuel was that it would be a powerful enough energy source for those who like to land on a planet without any items. But I “played around” with the energy stats and it backfired. Right now, I’m actually working on reworking this aspect. Solarite fuel will become much more energy-efficient, and it will be possible to combine it with uranium for use in nuclear reactors.