[jjcon]

Because significance thresholds can vary pretty dramatically. Plenty of experiments done in physics for instance have reported results even though they didn't yet reach a 5 sigma threshold (3x10e-7). In physics something can be highly highly likely but still not 'significant' enough to warrant a discovery. They simply couch it as, hey this was the result and even though it isn't 'significant' the high likelihood may warrant additional research here. Reporting a binary significant/not significant is far less useful.