Theories are quite necessary to our practice, because we all tend to think about what we do, how we do it and with what purpose. I believe the following small extract could give a clear idea of this:
"Translators are theorizing all the time. Once they have identified a translation problem, they usually have to decide between several possible solutions. [...] This private, internal theorizing becomes public when translators discuss what they do. [...] This does not mean that all our theorizing is constantly turned into public theories. [...] Only when there are disagreements over different ways of translating does private theorization tend to become public theory. [...] When those kinds of arguments are happening, practical theorizing is turning into explicit theories. The arguments turn out to be between different theoretical positions. [...] As theorizing turns into theory, some theories develop names and explanations for multiple aspects of translation, including names for the presumed blindness of other theories. When that stage is reached, it makes sense to talk about different "paradigms," here understood as sets of principles that underlie different groups of theories (cf. Kuhn 1962). This particularly occurs when we find general ideas, relations, and principles for which there is internal coherence and a shared point of departure. [...] Awareness of a range of theories might also help the translation profession in a more direct way. When arguments occur, theories provide translators with valuable tools not just to defend their positions but also to find out about other positions. [...] Since all translators are always theorizing, it would be quite wrong to separate the theory from the practice. [...] The real learning of theory, even for the self-learner, should be in dialogue and debate."
Source: Pym, A. (2014). Exploring Translation Theories. Second Edition. Routledge, NY.