Not to defend manufacturers--of anything--who put out bad quality products,
but I can understand occasional omissions in kit instructions. It is waaaaay more difficult to write good, thorough, complete, concise instructions than one might think--I used to write editing instructions for copy editors on rather complex publications. The hardest part was putting yourself in the shoes of somebody who's never done the project before and telling them everything they need to know without burying them in detail. (Misleading box art is less excusable, and attributing it to overzealous marketing dept. will do nothing to lessen the purchaser's disappointment!
)
That said, once a manufacturer finds out about an error or omission in his kit instructions, it really is his responsibility to correct it ASAP. Reprinting all the instruction sheets may be too costly, but certainly a photocopied correction sheet should be packed in each kit. I've seen those.
This is the long way of agreeing with upnorth that--dang it!--it sure is frustrating when something gets goofed up on your prized model because the instrux led you astray, and--hey!! I've got that Monogram B-36 on my shelves. Note to self: Reinforce the wings. (Thanks, upnorth!)
There are a few ways to minimize nasty surprises: before you dive into a kit, check for an old FSM Workbench Review and post a query on this forum for hints from those who have tackled it before. Dry fitting parts before applying the glue helps in a lot of situations, though I learned that rule the hard way more than once....and still insist on testing it more often than I should.