A standard is a promise the firm has made about how the work will be done. The promise is held when nothing tests it. Most firms hold standards in fair weather, and most firms believe they will hold them in foul weather too. Few do.
The standard is tested when the cost of holding it becomes real. A counterparty pressing for a faster answer than the work supports. A counterparty offering more for a compromised version. A moment when bending the standard is, technically, defensible. The pressure is always specific, always reasonable in context, and always cumulative.
Firms that drift do not drift in one large decision. They drift in a sequence of small ones, each defensible alone. After enough small concessions the standard is no longer present. It has been replaced by the average of what the firm has agreed to do recently. The drift is invisible from inside the firm. It is obvious from outside.
The firm that holds the line is the firm that has decided, in advance, what the standard is and what it will cost to defend it. The decision is not made in the moment. The moment only reveals whether the decision was made or not. Standards are not maintained by reaffirming them. They are maintained by paying the cost of holding them when paying is the harder option.