Why ionization energy and electron affinity are calculated in gaseous state?

Explanation

(i) Intermol ecular force can affect the value of ionization energy and electron affinity.
  (ii) In gaseous state, there is little intermol ecular force in a substance and it can be considered negligible in some cases. So the value of I.E and E.A are almost unaffected if they are calculated for gaseous atoms.
(iii) When we are talking about ionization energy and electron affinity, we need to consider atoms and we can find free atoms only when the substance is in gaseous state.