Dunno, you end up with a monopoly (Taisai + Refresh = legendary). Look at FFXI and the scroll of Quake for instance, on Shiva it's around 500k but drops from one of two NM's who pop every 16 minutes, is the scroll worth 500k? Not really, it's worth about 25k tops but you end up with an over-inflated price on scrolls or scrolls which are worthless in price.

Then you get scrolls which are basically needed for a job to function properly, Quake you can do without (unless you want to proc yellow) but if you're NIN you can't go without Utsusemi: Ni which is around 1m gil. With that in mind you put off players who want to level NIN but can't afford the 1m for the scroll or players who level up NIN and skip one of their defining scrolls.

If I were to add up the total value of all my scrolls I have on my FFXI char (90 RDM/BLM/NIN 80 SCH) it would come to.... wheres my spreadsheet........ oh, not installed, err, over 9000 gil? Millions! It's why you see BLM's who ES + Sleepga and not ES + Sleepga II because they a) can't do the quest or b) don't have 1m gil.

Even on my RDM I don't have a complete set of spells and I never will do yet I've dropped millions on tools for utsusemi.

Obtaining a scroll isn't an achievement, it would make some jobs harder to play for people with limited funds, whilst rich chars won't notice a difference and just drop the gil, heck, unlocking the WS trials is a bigger achievement and people are skipping that, magian trials are an achievement, unlocking the latent on WS weapons, tangible things you have to put an effort in to to get the maximum potential out of an object, having to farm for 5 hours to get a scroll of cure 2 is just a hindrance to gameplay.