Why does running out of mana deactivate sustained spells?

[Vanguard]

I don't see the point of it.

[greycat]

Some of the sustained spells have a per-turn mana cost as well as the up-front max mana cost. They probably all use the same code. (I haven't looked.) So, if current mana hits zero, poof.

[Vanguard]

I've never noticed any that do that. Which ones drain a set amount per turn?

[registeringislame]

Neither. I'd rather it not cast spells if mana gets that low. It's a pain having to watch out for it.

[greycat]

Well, my mage is dead at the moment, so I can't actually look it up without rolling up another one. But I remember Telepathy (or whatever it was called) says it drains mana. Not that I've ever had a mage survive long enough to learn and use it.

[Shoob]

the three that do, iirc, are telepathy, invisibility, and thunderstorm.