Questions - Relevance of Stock Markets

Here are questions that swirl around in my mind from time to time. When I have given it more thought, maybe some possible answers may materialise.
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If a stock market is merely a price-fixing mechanism to identify the prevailing value of shares, then is it necessary to have an active stock market all week long?

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Why can't we, say, fix just 3 hours for price-fixing on Monday?

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Why make stockbroking an industry?

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Wouldn't life be simpler that way?