I've been following this thread with some interest as, 3 weeks ago, I attended my local model railway club for the first time. I am inclined to work alone quite happily and usually prefer to do so as a matter of course, so going along to a club was not without reservation. I was able to attend for 3 nights before I had to decide whether or not to join and have to pay membership.
Last night I made that commitment as what I found the club to be was; friendly, welcoming, inspirational and accepting. I have learned a great deal already and it has definitely upped my modelling output at home.
As to why I joined a club, well, I had reached the limit of my knowledge and wanted to learn from others, I know that there is a wealth of experience on this board and have always had helpful replies no matter which question I asked, but there is nothing like the opportunity to watch others and question them about what they are doing, also to be able to have a real time discussion about whatever it is that I need to know at the time.
I am also enjoying the social side a great deal too.