these two practices can make an individual feel as they have found the "ultimate" truth, one they were destined to find and this is usually through the use of drugs and meditation. However, most psychologist consider this a "delusion'.
I personally believe the main reason why people want to be in this altered state of mind is because just like Siddhartha, they want to feel inner peace, no pain, and one with nature. They want to get away from their daily struggles and pains or the gruesome memories that haunt them. The main difference between the use of drugs and the practice of meditation is the effect they both have on the body. 

blocking everything to focus on the self. When people are in such desire to remove themselves from reality to feel that state of mind, they are in need of running way from their problems in reality and the solution would be to reach that altered state of consciousness and forget about everything.One major difference between consuming alcohol & meditating or praying is health. with alcohol your liver dysfunctions, but through praying or meditating your in great health.Benefits from from praying is you reach that state in mind through purity, and you connect with your God. Through alcohol and other drugs its a different situation. You don't get what your looking for, and its definetly not through good health or purity. There's no downfall when praying or meditating, but when drinking alcohol or taking other drugs things fall apart after reaching that state of mind.