NEVER QUESTION THE IT GUY!!!
</joking>
Back in the day, some laptops / desktops had a hard time going into hibernation mode; i.e.: if the hardware came out before Windows 9x / XP came out - the hardware wasn't really designed for it. So either your office may be running older hardware or the IT guy is living in the past.
Unless there's a specific issue with a make / model of a computer, which would generally be known by the IT guy; any PC made in the last 5 years (after Windows 7 came out) should be perfectly fine.
Every IT policy is different though so if the IT guy doesn't want you to hibernate - don't. Then again, they should of just disabled it via group policy / active directory.