Shadow IT.
Companies can have reasonable cause to block things, or require processes for installing software, etc., but when those burdens become too much time or effort employees will find a way around it.
Almost a decade ago, the company I worked for didn't have good wiki software OR a good request system. My team had a linux server for the purpose of some primitive monitoring and automation of our systems. Apache was already installed...
Within a few weeks we operationalized a new dokuwiki installation, and not long after that we built an internal request system based on Bottle.py (since it didn't require any installation, only a single file).
Seeing that GPT-4 is so incredibly useful to the people I've heard talk about it, there will be employees trying to use it to increase their code quality, communications, planning, etc.
My current employer put out guidance specifically stating not to put any proprietary code into it, no matter how small, nor any confidential information of any kind (don't format your internal earnings email with it, for example).
That seems reasonable, and recognizes how hard it will be for employees to go zero-tolerance, especially if they don't have total network control over work endpoints.