Many people expect a perfect translation every time, a natural and fluid sentence in the target language that accurately expresses the exact literal meaning and associated nuances of each individual word in the source language. A little thought will show you that this is a utopia: there are always going to be cases where differences cannot be expressed precisely. A concept that doesn't really exist in the target language. A reference to a nursery rhyme. A familiar national supermarket chain. A sporting hero in one country who is completely unknown in the other (take speed-skating and cricket, for example, in the Dutch and English situations).
The translator, in the absence of any instructions to the contrary, has to find a balance between the two ends of the greyscale shown on the right: literal exactness on the one end, through to total natural fluidity on the other.
There has to be a tradeoff to a certain extent between literal accuracy and natural fluency. This is inevitable. You can think of it as a sliding scale, a greyscale from one extreme to the other as depicted on the right. And each extreme also has its flip side: to keep the text running smoothly, some nuances may have to be modified or some aspects may need to be localized. Conversely, the more literal the translation is, the greater the risk of it sounding forced or stilted or "translated" - even when there is absolutely nothing wrong with the grammar. You simply can't always have it both ways.
You can see the problem: where should the blue arrow point in the diagram on the right? Our default approach is to position it to the left or right of the greyscale, depending either on the client's instructions or our experience of similar work. Or our experience with the individual client, of course. But when it's a new job for an unfamiliar client, you simply have to take the middle ground. Indeed, on the rare occasions that disagreements arise, they often boil down to someone expecting the arrow to be positioned differently... or expecting it to point to both ends of the scale at once.
Experience does of course tell us that particular types of translation require an approach that is far closer to one of the two ends of that spectrum. If the patient information leaflet for a medication is being back-translated (i.e. a first translation is being put back into the original source language as a way of confirming its accuracy), then it is clear that a highly literal approach is required. Similarly, nobody is going to want to read a novel in which readability and style have been sacrificed on the altar of absolute literal precision.