Technically speaking, no you don't need it. However the game rains you with materias which basically saying: "Here's free upgrade for everybody!" so why not make a good use of it? It makes your lives and your group's lives easier in a long run. You don't even need to buy off from MBs because pretty sure you should have a plenty by now to attach. Except of course: overmelding, which is a moot at this point.

Quote Originally Posted by iVolke View Post
Why do ffxiv players always try to find some excuse to not do the bare minimum? This game has been shoving materia down our throats since Stormblood.
By the same logic, they don't even need the i510 gears too i495 is enough because that is the highest ilv requirement (Paradigm) for contents outside latest EX trial and higher end.