I'd see products such as these as optional add-ons, as has been said, these are models for gaming - but the choice/option as to whether or not to add additional detail to your models, while not essential, can only be a good thing.
While I agree that 1/35 provides a larger, easier surface on which to place decals such as these I would argue that they would provide a possible approach for models in our chosen scale. 1/56 doesn't, for the most part, have the level of detail of larger scale models - & that's fine, they're primarily wargaming models (that said, Rubicon do a great job in finding the balance) - so I'm not sure it would be as problematic as suggested - & even if it were, it is after all, your choice as to whether to use them or not.