Does Area effect magic?

[Merrickz he/him]

So this isn't a super important question but I was curious so thought I'd ask. Why are some investitures only effective certain areas and some can work at vast distances. This especially relates to Scadrial where we've seen Allomancy and Feruchemy work off-world (by Hoid), however, I think we can assume that Hemalurgy cannot work off-world as I find it impossible to assume that no one in millennia of searching wouldn't have noticed that metals steal powers. Anyway, I was wondering if this has been brought up or if anyone has any theories as to why this occurs.

[MacThorstenson he/him]

Actually, I believe that hemalurgy has the potential to be the most wide spread magic system, the reasons that no one has discovered it before are 1) its ridiculously complex, even the lord ruler couldn't discover anything new after 1000 years of experimenting. The odds of someone stabbing someone else in the right spots are extremely low. Also even if they managed to somehow get a charged spike, no one in their right mind would shove it though their eyeball. 2) It requires intent to spike someone, Ruin is able to provide that intent, or the person doing the spiking, but intent is always required, without prior knowledge of it, you could never actually spike someone in the right place, with the right metal, and stab someone else in the right bind point.

[Merrickz he/him]

Ah, that makes sense. So I assume that, excluding AonDor which is stated to be area specific most investitures won’t be area specific 

[Yata he/him]

Hemalurgy as @MacThorstenson stated works everywhere but as it requires Intent to be performed and it's actual complex to put in place. Nobody will discover it for case.

Returning to your question. All the Magic Systems are potentially usable everywhere (The Selish's one are weird because of Sel's state). But some requirements of the magic itself could not be so avaliable everything.
Some requires Investiture with a specific features, but if you have it...you could carry around and use it (Awakening for example),

other requires specific objects/beings not avaliable off world but again you could carry them from their homeland (Sand Mastery and Aviar)

still others comes to a symbiosis and one of the two parts has an hard time to leave the homeplanet (KR and Shardwielding)

The Metallic Arts are mostly the more portable because once you are a Metalborn, your other requirement is spread all across the Cosmos, while other portable magics will have problem to replace the requirement if lost (Awakening for example)

[Weltall]

Yeah, other than Selish magics which (within our current understanding) have a hard limitation on their use offworld, all forms of Investiture are at least theoretically universal even if some may be harder to use than others. For a rundown:

- Allomancy and Feruchemy: Usable anywhere as long as you've got access to the right metals, and it doesn't matter where the metal comes from.

- Hemalurgy: As noted above, it has Cosmere-wide application but you need Intent to actually create a spike so nobody is going to discover this one by accident.

- BioChroma: We know this can be used offworld both for the passive benefits of Breath and actively in Awakening. It's also the easiest systems to get magic from for a non-native as Breath is keyed to your Identity when you receive it. Though Brandon has said separately that Returning is pretty much locked to people born on Nalthis.

- Surgebinding: Could be done offworld as long as you have access to Stormlight, but it would require some knowledge to get the spren away from Roshar's Cognitive 'region'.

- Sand Mastery: Usable offworld and the sand can be recharged as long as light from Taldain's star is visible in your current location.

- Aviar: Usable offworld as long as you can keep the bird alive.