Identity NAT with Public IPs ?

Hello,

I took over a project to migrate an old ASA 5520 to a Firepower 2110 with FTD and managed by an FMC. The old ASA was having a bunch of identity nat for each of network, all networks being Public IPs.

My question is: why would someone do that kind of configuration? Translating a public network to itself when there is no private network in place for this organization.

I know that I can remove all the NAT rules and the FTD will continue routing all the public IPs fine, but I would like to know what the Security experts opinion is on this matter.

Thank you in advance.