I dunno, why?

Pictomancer is a very relaxed full-caster job. And I say this in a context of there basically being no full caster job anyways:

* Red Mage can move 50% of the time even during full casts, more due to the combos.
* Black Mage has ~30%-40% instant casts, can in fact run a near-full-DPS all-instants combo if needed.
* Summoner has four hardcasts in a while minute assuming you safe Swiftcast for emergency rezz, three casts otherwise.

Still, Picto is quite relaxed. It has no fixed rotation like other casters do (Summoner's ifrit-placement is the other exception I suppose). It has a movement tool that even completely randomly grants Sprint afterwards. It has a personal shield. It has a group shield. It does some minor support healing. It has as stationary buff, but unlike Black Mage the radius is super large so it barely confines you in the first place. It's rotational constraints are freeform-placed between other casts. It overflows in on-demand instant casts because it keeps a steady supply of them around (not like Red Mage where you don't want to overcap and hence usually only have one for movement purposes). Only these flexible motifs are slow to cast, everything else is comparatively quick. It genuinely likes downtime and getting out of combat between pulls, which other casters hate because it messes with their CD alignment. For Picto, it's free motif recharges!

The job is so player-friendly, you could genuinely argue Summoner is more difficult to play, at least that has to keep some CDs aligned to a rough degree. I'd say Picto is still more difficult, but not by a lot. There's little excuse for it dealing anywhere near top-end damage, more so because of the extra utility options it has to keep a Picto from dying and hence causing a wipe, something other jobs don't enjoy.