Any reason for the zzrot nerfs?

Zzrot isn't a massively purchased item by champions other than singed and heimerdinger as well as the occasional lane pushing tank but I don't think it is so good that it's duration needs to be nerfed by 60 seconds.

This means the portal will require more frequent placing and will often make the buyer need to spend more time not grouped counterintuitive to the use of the item. I don't understand what the purpose is for this, if someone would enlighten meit would be very much appreciated.