Having thrown a good number of parties and events...
Of course "whatever stupid event it is, is just an excuse to hang out with people. "
But its just... easier... if you can give people an excuse to let themselves go. A lot of people are really nervous around strangers, and its not the booze so much as the comfort it provides. It gives them plausible deniability for their actions, and thus loosen up enough to actually enjoy themselves. Hell, I've seen it work where all the booze was replaced by fake booze - a lot of "drunkenness" is acting, and most people won't notice unless they are trying to get more than tipsy.
And a lot of others, like myself, don't NEED an excuse to hang out with people. I tend go to events if the activity its based around interests me - the social aspect is just a bonus. If I really want to hang out with people, I phone around until I find two or three other people that are interested and then we go hang out. People who need an "event" to hang out with people are generally the same sort of people who probably need the alcohol.
Now, I have had a few successfull large-scale events without any booze at all, but I find these tend to work best when you give people a real reason to come - something a bit out of the ordinary. Also, look at the background of your friends - theatre people and gamers tend to really get into murder mysteries, and you can usually use them to form a solid and reliable core. Foodies and adventurous folk can be tempted with a party centered around some exotic food like miracle berries. Basically, you need something that will convince the people who attend they have something in common with each other, and REALLY give them an excuse to come if they don't want to feel like they went just to socialize.
If you're aiming for larger groups, like 8+, when inviting people, aim for "cores", the sort of people who sort of steer their own little social groups. Don't just invite people at random, invite the people who can inspire others to join who were on the fence. Keep in mind that many people are lazy and poorly organized. Plan at least a week in advance. Call once before the day and the day of to make sure they are still coming, especially if they are a core participant. There are a surprising number of people who want to come, who really would enjoy coming, but just don't really feel like dragging themselves outside to do it. Give em a push and help em along, but only if you think thats the reason - others really would just rather do something else.
I don't really know where I'm going with this though, on account of the derail and the fact that I'm not really sure what the original post was about.
Edit to add:
Sometimes events flop. Something else more interesting comes along the same group wants to go to, or people just get busy, or there's inclement weather, or a host of reasons. Usually, though, it's because the person planning the event.