Our organization actually does really well with IPAM as a whole for the internal private IP side of things. I cannot speak to the public IP space, but have yet to see an issue with it.
While we have a few different teams with access; typically only one team assigns out IP addresses and they are the ones who build out servers and network gear so it all works out 
ETA: I can also attest to the "total cost of IP conflicts" mentioned earlier. My last organization had this problem constantly as we had a single spreadsheet on a SharePoint site with IP addresses, that no one ever used 