Pourquoi est-ce que le imparfait est utilisé dans cet exercise? imparfait

Raymond, 

assuming you mean in the clauses following ‘ comme si …’ , these are hypothetical statements and clearly unlikely to be true. It could also be considered as the expression of opinion rather than fact. 

These are typical uses of the imparfait - remember it is not just a ‘  past tense ‘. 

See links below :

 https://www.lawlessfrench.com/grammar/imperfect/  ( under ‘ si clauses ‘ for ‘ comme si.. ‘ example ).

 

 Expressing opinions and describing with the imperfect tense in French (L'Imparfait)