My reason is that audit sites don’t work properly when name changes occur. I switched similar names between my two accounts, hence why any shitty sites will show that my account suddenly grew from 7k to 85k. (I then switched them back. Thought one was more catchy than the other and then changed my mind.)
If you want to know the name of the 7k account which I still have access to I’ll happily PM it to you.
Edit: This is largely due to the updates Instagram introduced early this year, which disabled tracking of follower growth, hence leaving enormous gaps on account growth or leaving accounts that were never previously searched on the site before as untracked. ex. socialblade