Why Islam prohibits alcohol?

Alcohol is the mother of all evils. It intoxicates and causes a person to lose his mind. Alcohol inhibits the inhibitory centre in the brain, causing a person to behave erratically. It is the root cause of adultery, rape, fatal road accidents and several other crimes.

Allah says:

They ask you about wine and gambling. Say, "In them is great sin and [yet, some] benefit for people. But their sin is greater than their benefit." And they ask you what they should spend. Say, "The excess [beyond needs]." Thus Allah makes clear to you the verses [of revelation] that you might give thought. [2:219]

O you who have believed, indeed, intoxicants, gambling, [sacrificing on] stone alters [to other than Allah ], and divining arrows are but defilement from the work of Satan, so avoid it that you may be successful. [5:90]

It was narrated that Abu Darda’ said:
‘My close friend advised me: ‘Do not drink wine, for it is the key to all evils.’” [Ibn Majah]

It was narrated from Ibn ‘Umar that the Messenger of Allah said:
Wine is cursed from ten angles: The wine itself, the one who squeezes (the grapes etc), the one for whom it is squeezed, the one who sells it, the one who buys it, the one who carries it, the one to whom it is carried, the one who consumes its price, the one who drinks it and the one who pours it.” [Ibn Majah]