Why are 'eternalism' & 'annihilationism' mentioned in SN 12.17?

In SN 12.17, it is said: > *Well now, good Gotama, is suffering caused by oneself?* > > *No indeed, Kassapa," said the Blessed One.* > > *Well then, good Gotama, is one's suffering caused by another?* > > *No indeed, Kassapa.* > > *Well then, good Gotama, is suffering caused by both oneself and another?* > > *No indeed, Kassapa.* > > *'He who performs the act also experiences [the result]' — what you, Kassapa, first called 'suffering caused by oneself' — this amounts to > the Eternalist theory.* > > *'One person performs the act, another experiences,' — which to the person affected seems like "suffering caused by another" — this > amounts to the Annihilationist theory.* Alternate translation: >*Kassapa, if one thinks, ‘The one who acts is the same as the one who > experiences the result,’ then one asserts with reference to one > existing from the beginning: ‘Suffering is created by oneself.’ When > one asserts thus, this amounts to eternalism. But, Kassapa, if one > thinks, ‘The one who acts is one, the one who experiences the result > is another,’ then one asserts with reference to one stricken by > feeling: ‘Suffering is created by another.’ When one asserts thus, > this amounts to annihilationism. Without veering towards either of > these extremes, the Tathagata teaches the Dhamma by the middle: ‘With > ignorance as condition, formations come to be; with > volitional formations as condition, consciousness…. Such is the origin > of this whole mass of suffering. But with the remainderless > fading away and cessation of ignorance comes cessation of volitional > formations; with the cessation of formations, cessation of > consciousness…. Such is the cessation of this whole mass of > suffering.*’ Why are 'eternalism' & 'annihilationism' mentioned in SN 12.17 when SN 12.17 does not appear to be directly about reincarnation or about the denial of reincarnation?