[Faceman]

they are for cutscenes, quests, etc.
for example there are spell versions of Finger of Death or Power Word Kill for the cutscenes where Irenicus kills some Cowleds. These do not allow saves, magic resistance,... because it would be plot-stopping if a cowled made his save in a cutscene. Some spells don't have an effect but only an animation again to provide pretty looks in a cutscene while the effects are scripted.
Some spells (earthquake in the underdark) are needed for quests and have very specific effects you never need afterwards,...