For certain things, there are guidelines to establishing residency in each state and moving to that state and having a ID alone is not enough proof for the state to consider you a resident. I just moved to another state recently (about 8 months ago) and for example, school in my sitution, would not allow me to pay resident tuition fees as I am still not considered a resident. I would only qualify for non-resident fees until I meet the residency guidelines which include but are not limited to “physically” residing in this state for 12 consecutive months along with some other requirements of proof (ie. employment, taxes filed, dwelling, etc..).
Each state is different, but it depends on the extent of the case residency would need to be addressed. I know for other things, I just need to show my state ID and I’m good for discounts.