Because there might be some other programs with a lot of computational resources which scan through simple universes looking for programs to run?
More like: because there is some chance that the actual laws of physics in our universe execute data as code sometimes (similar to how memory unsafe programs often do this). (And this is either epiphenomenal or it just hasn’t happened yet.) While the chance is extremely small, the chance could be high enough (equivalently, universes with this property have high enough measure) and the upside could be so much higher that betting on this beats other options.
More like: because there is some chance that the actual laws of physics in our universe execute data as code sometimes (similar to how memory unsafe programs often do this). (And this is either epiphenomenal or it just hasn’t happened yet.) While the chance is extremely small, the chance could be high enough (equivalently, universes with this property have high enough measure) and the upside could be so much higher that betting on this beats other options.