Strength in numbers
Each person who chooses to resist mass surveillance with encryption makes it easier for others to resist as well. People normalizing the use of strong cryptography has multiple powerful effects: It means those that truly need it, like potential whistle-blowers and activists, are more likely to learn about it. More people using it for more things also makes it harder for surveillance systems to single out those that can't afford to be found, and shows solidarity with those people.