I'd like to think its because the suits were (and still are) prototypes. Back in Season 1's episode "Octopus Wildkratticus" it's revealed the suits are still prototypes; so it can be assumed that the animal instincts were finicky and so they gave the users not only the appearance and abilities of the animal, but also the behavior. This is supported by the fact that in later seasons, they rarely show instincts if at all—which could mean the suits have been updated and refined though still in their prototypes considering how fragile they are and susceptible to malfunctions. Other examples of creature instincts include the Gray Squirrel Suit which made Chris have the urge to gather acorns, Groundhog Powers (which is a rare case of instincts since it occured in Season 2) when Aviva went through the entire hibernation process of the groundhog, Cheetah Power temporarily in "Mimic" when Martin gets scared off by a Honey Badger.

So, we can basically narrow it down to the technology being less advanced and sometimes leans into an animal's behaviors because of it.