Mana management is very present for some classes/roles. Aside from BLM, DRK, RDM, PLD, it's especially relevant during progs, MINE duties, which include the first few weeks of the newly launched current savage, ULTS, and when you die or multiple people die.

I always have to carry mana pots with me. Different SPS builds will require you to have mana pots available to be able to maximize both DPS and shielding/healing even outside of prog. Even using mana pots sometimes is not enough to sustain upcoming mechanics if I die for whatever reason.