My favorite advice columnist has taken a stance I'm not entirely in agreement with. That it's not ok to say one will attend an event, then cancel for anything other than an illness, emergency, or very specific set of one time events. The original question wanted out of a work party for 40 people to attend a friend's birthday party. I know which I'd choose.
For me, I would never attend another RSPV event, other than a wedding. And I feel I have every right to dump out on any social gathering to which I have been coerced into agreeing to attend. Work parties are always of that nature, it's infinitely easier to no-show than to tolerate the barrage of "OH, but you HAVE to go!"s for weeks preceding. Had I figured this out sooner, would have saved me my second year at Famous Boston Hospital. I'd attended the department Christmas gala the first year, and despite wearing the most dressy clothes I have ever owned, was grossly underdressed. Not to mention not getting chat with anyone I liked, and that sucky band. The next year I had no intention of going, and everyone, EVERYONE, badgered me to attend again, including women of quite different shapes offering me their spare dresses. I should never have admitted I wasn't going, since I looked like the wet blanket party pooper. Fairly, but very uncomfortably.
I figured out how much I hate work socializing, and how impolitic it is to bluntly refuse. So I will always make vaguely assenting noises, and will never go. Hosts can just suck it up.
Maybe the reason so many people skip these formal events is the same reason I do. People who really love parties, especially the big fancy do's with elegant clothing, uncertain music, excessive alcohol, and rich food, with way too little actual friendship and conversation, are a minority. And us introverts, pressured into saying yes, often can't stomach the idea of actually going. Even just a large, loud blow-out lacks what most people like me want of an evening. I have enjoyed perhaps three parties, in my life. Not great times, but I got to talk with friends, and laughter abounded, so, yeah, good. On the other hand, most of the worst moments of my life have been at parties, tearful among balloons and neighborhood children. Or a bit older, tired and stuck, later - drunk and vomiting. Why else do so many drink at large festivities, but to drown the anxiety? Largely, mostly-wastes-of-time. So, a while back when everyone was planning food and drinks to meet on a weekend, they asked if I was going. I said, "That's the plan." I stayed comfortably at home.
It does bother me a bit, because I prefer not to lie about anything. When I say I will be somewhere, I will be there, usually early. But something that is supposed to be fun and voluntary, that fails on both points, falls into the category of Trick Question.
Get-togethers with friends, spontaneous, or at least very informal, can be wonderful. I like hanging out with friends, with conversation and shared ideas. Like when we meet up in San Diego next month. Completely different experience.