When to use te form and past tense


Was going through my Genki book and saw an example sentence of te form verb
but it ended in past tense. (言う いってた) Why use the te form at all and not just
past tense

> 「あきらさんは何て **言ってた** ？」  
>  「チョコレートを食べすぎたって **言ってた** 。」




I think which version you use depends here also on the continuity of the
action.

Maybe compare:  
「...彼は言った。 」  
「...彼は言っていた。 」

With:  
"He (once?) said..."  
"He used to say..." OR "He was saying..."

