I've learned on the Sailor Moon subreddit that these long transformations, introductions, and yelling out your attack name and your own name that you often see depicted in anime actually stems from samurai culture. Samurais would have people helping them change for a fight right before the fight (transformation) and it was considered manners to introduce yourself at length to your opponent, so that if they brought your head home, they could say who it was whom they defeated - and vice versa.
Considering the power rangers are somewhat american and japanese and produced by toei, it would align with that idea.
(yes I know, I must not mention reddit here, but it's really such a wholesome community in that one sub, please keep the hate out of r/sailormoon ๐ญ )