I think it's to combat the colloquial definition of "significant" with the specific statistical definition. All polls and samplings have an amount of error (e.

I think it's to combat the colloquial definition of "significant" with the specific statistical definition. All polls and samplings have an amount of error (e.g. Biden leading in the polls at 30%, 3% margin of error). If Biden polls at 32% next week, there was an increase. Colloquially some would say that's a significant increase (after all, his pie grew by 6% compared to the prior week!), but it's very likely to do with chance. Unless you survey the entire population, you don't know the true proportion in which something occurs. A change from 30% to 35% is quite unlikely to be random chance.