I can see that, LaFemme. It's easily accessible, legal, doesn't carry the social stigma of harder drugs, and as such, as Supercrew noted, can sneak up on you before you know what happened. It also lowers inhibitions, making you more likely to try something you ordinarily wouldn't. I read somewhere that the two drugs most often abused in tandem are alcohol and cocaine, basically because the coke takes the sleepiness out of being drunk so you can drink all night.
Personally, I went from alcohol to meth, that was the first illegal drug I ever tried. I didn't do softer drugs like pot until a couple months after I started doing meth, and then only because someone happened to have it while I was waiting on my dope to show up at my dealer's house.