You can break up the monotony of making the same item a million times by switching between classes and making collectables from each. Even leves would end up monotonous as a scrip grind after a while because there would be a "best" item to make (like Coffee Biscuits were for gil in Shadowbringers, it also got complaints for being boring).

Leves are there for the players who want to be earning gil instead of scrip. Collectables are there for players who want scrip instead of gil. We know SE isn't inclined to reward scrip and gil from the same source other than Custom Deliveries because collectables used to also reward gil in addition to scrip and SE removed it.