There is a relevant quote in AN8.39
AN8.39: Abhisanda Sutta wrote:Furthermore, abandoning the use of intoxicants, the disciple of the noble ones abstains from taking intoxicants. In doing so, he gives freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings. In giving freedom from danger, freedom from animosity, freedom from oppression to limitless numbers of beings, he gains a share in limitless freedom from danger, freedom from animosity, and freedom from oppression. This is the fifth gift, the fifth great gift — original, long-standing, traditional, ancient, unadulterated, unadulterated from the beginning — that is not open to suspicion, will never be open to suspicion, and is unfaulted by knowledgeable contemplatives & brahmans. And this is the eighth reward of merit, reward of skillfulness, nourishment of happiness, celestial, resulting in happiness, leading to heaven, leading to what is desirable, pleasurable, & appealing; to welfare & to happiness.
The term translated here as "intoxicants" is in pali "surāmerayamajjapamādaṭṭhānā". The last part of this word, "pamādaṭṭhānā" gives us an idea of the reason why: they are substances that are a cause of "pamāda", or heedlessness. The path taught by the Buddha, the Noble Eightfold Path, has the Deathless as its goal. As the Dhammapada tells us, this requires heedfulness, the exact opposite of what intoxicants create.Dhp II
Dhp II wrote:Heedfulness: the path to the Deathless.
Heedlessness: the path to death.
For a full essay on the importance of heedfulness in the practice, you can read The Practice in a Word
by Thanissaro Bhikkhu.
From a lay practice perspective, it can be informative to read DN31
DN31: Sigolavada Sutta wrote:"There are, young householder, these six evil consequences in indulging in intoxicants which cause infatuation and heedlessness:
(i) loss of wealth,
(ii) increase of quarrels,
(iii) susceptibility to disease,
(iv) earning an evil reputation,
(v) shameless exposure of body,
(vi) weakening of intellect.