For two reasons.

The first answer speaks for itsel: This means the rules you follow and the precepts you are taught to live by. However, those rules could be right or wrong. Philosphy enables you to decide and rewrite them for yourself in a sane and useful manner.

The second is more a matter of psychology. We have a central nervous system and a co-ordination system that is the best on the planet. By it's structure, it seeks to expand its range, depth and scope of things under ordinary circumstances. It works by processing data from the senses or instruments into wholes that work. UNless you really beat a person down, which is an aberration of the norm, this is what the faculty called the mind will do.

Prior to the discovery of the neural synapse by James Olds, it was believed that drugs offered a route to mental expansion. One of the Huxley's wrote of peyote, The Key to the Doors of Perception. In the Dune series, the drug called variously "spice" and "melange" was termed in the scientitic lingo the "spectrum awareness narcotic". However, with the discovery of the synapse and the mapping of the brain, we found that durgs, particularly hallucinogens. only caused synpses to fire, they did not offer any kind of mental upgrade. the key to addiction is not the physical action of the drug, it's the brain state, or in the specifically observable case of smoking, the conditioning by what is going on around you. I used to smoke a half-pack a day. Under certain circumstances, when I was with other musicians and we were having an intense session, even just at someone's house, in a hevy-duty philosophical discussion, or anything that I got very into, I'd do a good fraction of the half-pack in the afternoon. Here's how I ended up quitting. I made the conscious decision that I enjoyed smoking as an adult. I also knew that it could take over the show. I then made a decision that if I reached the pack a day level I would deal with it. Well, that happend in 15 years in 1986. I decided to stop for a while until I could set it back to a half-pack. Well, when the time elapsed and I went to start back, I found I really didn't like it all that much. so I stayed off it. Like most drugs, nicotine clears the system in 72 hours. The remaining cravings are more a result of conditional responses ("classical conditioning"). What I did that was clever was consciously retained the control option and set the definitions of the terms by which I would excercise it. The nicotine was never an issue with me, it was that the act of smoking had become part of the scenery of the other things (talking, playing etc, and how it made me feel). In 1971, I experimented with pot. The issue was controversial, I am curiosity-driven and there was, given the survival rate, no significant danger, so why not? The first time, nothing happened (I did not know what to expect), second time, same deal. then I upped the ante to hashhish. well the guys around me were really stoned: Me? no soap (and we had the classic phychedelic Iron Butterfly record on, too). the third time I tried grass I was fooling aroud with a kaleidoscope (if that didn't do it, nothing will) well what happend perceptually was that I felt drawn into the image and my sense of time went flukey. I decided two things:

  1. I could do and have done this kind of thing anytime I wanted so the pot added nothing I needed
  2. I didn't like my sense of time going out on me so the pot gave me something I neither needed nor wanted
So what of those who seem to need the fix? It seems to me that the mind, will fill the gaps and invent things to deal in the higher levels of abstraction and range expansion. The effect of the drug is to appear, from the inside, to do that, which is why, in the late sixties, persons who used the "psychedelic" drugs were called 'head"'s and the places where you got the cultural accutraments (incense,lava lamps, fancy color-changing lights, strobe lights, all of which I eagerly devoured and still love. I used to run the light show for a local band before I even touched Mary Jane, and would do it again) were called "head shops". Having ones mind "blown" is a rather pleasant experience. I was one of the biggest "head"'s in the area and I was totally straight: this was the unkept promise of the late 1960;s. It led to my half-joking quip: "algebra should be studied while stoned.". By that, I meant that it will challenge and expand the mind, in essense "blowing" it.

What all of this says is that the brain is so constructed that, no matter what, it will seek to expand awareness. Either it will do so in a systematic, organized manner or at randome; the integrating mechanism is a built-in function. Therefore it needs a control system like a missile needs a guidence system if it is to be accurate. Just as a computer needs its "operating system": The programs that tell it what to do, the faculty of mentality needs an operating system to instruct it in what to do. Philsophy writes that operating system. The "will to believe" is very different from the "will to understand". Because it writes that operating system, philosophy is something that reaches to the very core of how we think, approach the world, calculate good and evil and other such matters. As such, it too, is a mind-blowing experience. And the reusults are useful: the proper philosphy will upgrade the mental functionality by up to 30%.

So that's why you need-and ought to enjoy, even get stoned on, this crap.