过去式过去分词的问题concisely explain why the past participle(过去分词) an

It's simple!The "past participle" refers to a finished status of a matter or its passive situation.And the simple past tense only repeats that a matter did happen before.
So,it is easy to understand why it is necessary to consider different forms for the verbs:they express the different status of a matter.
I wish this answer could provide you a better understanding in using different forms of English verbs to express an idea right:)

A past participle is not a verb, and must either be used as an adjective or in conjunction with a verb (to BE, to HAVE, etc.), while a simple past tense is a verb.
Detailed explanation:
A past...