I think whether or not its necessary depends on the person. In itself, obviously, alcohol is not evil. It is a neutral substance. It has medical uses in some forms, it has some health benefits in other forms, and yet ingested in excess, especially repeatedly, tends to have negative consequences up to and including sickness and death. Alcohol can be medicine for both mind and body, for example a drink used responsibly to alleviate stress not only relaxes the mind, but in turn relaxes the body. The poisons of hatred, desire and greed for example have biological equivalents that weaken the body and make it more susceptible to various diseases of both mind and body. So drinking can have a medicinal effect on ones state, even increasing ones ability to perform meditation or a daily practice of some kind.
On the other hand using alcohol frequently to relax in such a way begins to become a crutch. Using it for fun opens up an entirely separate can of worms. When you drink to the point of intoxication, you are playing with fire. Maybe you can maintain mindfulness, maybe not. You say you will just have one or two, and it turns into five or six and a shot. You say you will only spend 20$, and you end up spending 80$. So begins a cascade effect of saying you will do one thing then acting in the opposite way as a result of how the alcohol is influencing your decision making process. True mindfulness is aware of this process and therefore would not make decisions based upon it. Sure, its possible to maintain Rigpa (for example) while drunk and high even. Every state of body-mind related experience is based in chemicals, and there are biological effects that can be experienced from meditation and other practices. From this point of view its not like one chemically induced experience is more valid, real, substantial or permanent than any other. Although mother nature might have chosen this one particular arrangement, it doesn't mean other arrangements and experiences are inherently wrong. The mind influenced by LSD is capable of permanent realizations about the nature of the mind or reality. There are paths that include drug use of various kinds that lead to various siddhis and states of enlightenment. Theres no real absolutes that we can lock down in regards tor right or wrong with alcohol or anything else. We could create an arbitrary rule that we choose to follow, saying for example its all OK as long as positive results come from it. Once a negative result manifests, we should consider giving it up. It seems inevitable that a negative result will eventually manifest whenever any substance is used enough. Then again I think the inevitability of a negative result is just samsara in a nutshell.
Either way we are always playing with fire whenever we begin to alter our chemical state in extreme ways. One moment we are fine, then we lose mindfulness and suddenly we are saying or doing things we will later regret, even if only mildly as social humiliation. I know this from experience