But as above, if Tritium should regenerate quickly enough that it might as well have infinite supply, why not just use Credits as fuel instead?
Well, realism, I guess. Having to fill your tank with something in preparation for a long journey makes sense. Also, I was actually looking forward to planning the placement of tritium tankers for a deep-space expedition. Magically-appearing fuel would remove that.
Personally, I'd like to keep the logistics of actually getting the tritium from the infinitely-regenerating supply point out to the Carrier, rather than placing it ON the Carrier.