But I might need it later? Easy.
The biggest and rarest support items for an RPG are to be used LAST and as an EMERGENCY. All those Elixirs and Mega-Ethers and what-have-you that replenish the characters back from ANY state of being (including death) are the last resort devices and not to be wasted.
Why? Because there's so few of them, usually. Do you know how many SP-refilling items you usually find in Persona 3 or 4? FEW! Against the whole of Tartarus or the TV-World, these items are puny and or lacking or even too important for spur-of-the-moment. Our characters are gas-guzzlers, and they don't always sell the stuff you need in shops.
So, in the case of at least some RPGs, it's not a matter of 'might', but 'will'. You WILL need it later when Lord Scumflagon of the Infernal Destiny comes calling with his massively huge attacks. That's what they're there for.