good point on the second paragraph, that's why all reviews happens in between each iteration

you agree that it takes more than googling to make this choice although it might be a sign of efficiency if it is used widely but again its case by case basis argument

a few comments on the line "Because they can be elected and used according to our tastes." this depends who "we" are and where "we" fit in within the organization hierarchy.

managemenent is not the place to decide on the methodology, although they provide the input like anyone else but they more interested to play with dates and numbers :)

these practices are a common decision made by more than one team of responsibility (QA, PM, CSG, etc). how you deliver a product to customer? this is a key driver to the decision or how the product is going to be released. I'm not trying to make this complicated but once again this is project size and strategy dependent. as you said they are both useful.

funny enough, I have seen very critical projects  (not very big though) that had absolutely no documentation or specific process  and seems like they are doing pretty well - don't ask me how cause I don't know

and about standards, don't forget that standards are written based on real experiences and even they are versioned (don't they?) so decision makers have to be flexible. organizations consider the theory and conventions and implement their strategies to be aligned with their needs in another words, create you own version of e.g. RUP and never publish it