這英文句子 為何這樣寫?

I request that further investigation be conducted.

The sentence expresses a demand making the verb form of suborinate clause ( "conduct" in passive voice) to be in subjunctive mood (虛擬語氣).

"is conducted" (indicative mood, present tense)
"should be conducted" (indicative mood, modal)
"be conducted" (subjunctive mood, present)

Grammar Note:
The subjunctive mood is the verb form used to express a wish, a suggestion, a command, or a condition that is contrary to fact.

Verbs attracting the Subjunctive Mood:
The following verbs typically followed by clauses that take the subjunctive:
ask, demand, determine, insist, move, order, pray, prefer, recommend, regret, request, require, suggest, and wish.

回答者： Julie 已經解釋很清楚句子是用 subjunctive
It is a joy to read her writing.

謝謝來郵, 只作補充
request (v) 是 formal verb, ~ to ask someone to do something in a polite or formal way.
(相反的, 用 demand)

Subjunctive is often used in very formal language (regulations, legal documents)

2015-06-11 20:13:47 補充：
She requested that no one be told of her decision until the next meeting.
( BrE also ) She requested that no one should be told of her decision. ~ 牛津字典

We require that all receipts be submitted to the committee for approval.

I know not whether laws be right,
Or whether be wrong ~ Oscar Wilde