I work in the science field... One the title of Theory does not mean unproven (though it is argument most give by those of a religious nature against them), Theories do not grow up to become Laws they explain them. Einstein's Theory of General Relativity explains the Law of Gravity, but there will not be a law of General Relativity. The title of Theory goes to something that hasn't been disproven, if a Theory is disproven it will be replaced. The Many-World Theory and String Theory can not be disproven only because we lack the ability and understanding to do so it may belong more in the province of scientific philosophy and regain the title of Interpretation and not Theory. Giving them the title of Theory brings down the Theory of Evolution, the Big Bang Theory, and so on for those such as religious groups to point and say that they are just "Theories".
Most equate the idea of religious belief system as something of the dogmatic structure of the abrahamic religions but they are not the only example have religions they are just the most dominate ones. The idea of faith and belief does not require a ridged dogma to exist.
I'm not saying that physicist worship at the Temple of the String or read for the Book of Multiple Earths on a pilgrimage to Copenhagen while singing hymns to Bohm . But the ones that do work in that field have to have some kind of belief or faith when applying them as theory as they have not been through the scientific vetting process and believe their outcome has a scientific barring if it cannot be challenged.