Hello Anon,
Sometimes you need the past tense. The present perfect won't work in every situation. Sometimes you need the past perfect too.
For example: Pretend you want to describe a situation in which you went to a party hoping to see someone. That person was at the party, but left before you arrived. You cannot use the present perfect: *I have gone to the party but when I have gotten there he has gone. Do you see? You need to say I went to the party, but by the time I arrived, he had left.
You also don't use the past tense with a specific time in the past. You do NOT say: I have eaten there yesterday, or I have watched my daughter's volleyball game last Saturday.
When you reply, so I know you have seen this, I am going to move it to the Basic Grammar section, okay?