LML -- When you have a chance, please consider clarifying whether your reference to bad meals is to meals that a member knows will not meet his standards before the meal, or to meals that in hindsight are not as expected.So do I. However, far more space here is dedicated to saying why things don't work than why they do. Although the latter is far more interesting and worthy of attention, it is also a great deal more difficult to do.
You surprise me. I mind spending a fortune on a bad meal, regardless of whether it affords an opportunity for erudition. I shouldn't have thought there were "many" people who fit your description. But who knows?
My own experience is that I expect most restaurant meals I plan will not be rhapsody-inducing. That is because I know my own preferences quite well, read considerably about restaurants and can deduce quite a lot from menus on their websites (if any). However, for certain restaurants I have never tried in my life (including restaurants that I know would very likely not provide stunning experiences, which comprise many restaurants I visit), I want to have visited them at least once in my life to satisfy my curiosity about them. Bux has mentioned this type of curiosity in another thread. For me, it's not a question of wanting to visit this type of restaurant to be able to say to third parties I have done so. I also enjoy comparisons across different restaurants, and so visiting new-to-me restaurants sometimes triggers thoughts about all sorts of cuisine-related and restaurant-related matters. I even enjoy the process of choosing known non-wonderful restaurants, and, yes, after a meal at such restaurants, I may have criticisms that are posted along with any positive aspects.
Also, I (and presumably other members) do not post about every meal taken. What I post on reflects many factors, including perceived level of interest on the board (e.g., when I visit Craft or locunda locatelli for the first time, I am likely to post), personal quirks, time constraints based on the demands of work, friends and family at any given time, personal energy level and many others.