I'd say it's more of a security concern than anything. The thinking being that you don't want a potentially disgruntled employee with little to potentially lose have access to your systems.
I was sure someone would say this. As a comparison: Romania is a relatively poor country, full of hotheaded invididuals ("Balkan" mentality). On top of that, we're apparently EU's #2 expat community in terms of total prison population. So both hotheads and also a lot of criminals (most likely thieves).
And yet we still allow our folks to walk unescorted for a few weeks inside the company premises.
After all, how many just-layed-off employees will want to steal or damage company property to top off their recent loss of job with criminal charges and a criminal record?
From the outside it feels like a bit of paranoia on the part of US companies.
I might be missing something, this is just my opinion as an outsider.
Let's consider the counter-argument and ignore any possibility for vandalism, theft, hacking, or other destructive activity by a recently terminated employee. Why would you want them walking around the building? What possible benefit is there to this? Why not just give them a hearty handshake, a thanks for your work, and tell them that they will be paid for the remainder of the termination period but don't show up at work tomorrow.
As for the paranoia part, it is definitely a bit of paranoia on the part of the company management but paranoia for a reasonable reason: there are numerous examples in the US of someone getting laid off or fired and returning to the office with a gun. From the perspective of management, why take the chance? If there is any hint that the termination will not be pretty you make sure someone escorts the person out and you have shown yourself to be taking due consideration if something unpleasant happens.
Non USian here: regardless of who gave notice, the lame-duck period is normally used for wrapping up whatever work/project the departee was working on and handing it over to a colleague or manager. People generally are more worried about getting bad references than office shootings.
And yet we still allow our folks to walk unescorted for a few weeks inside the company premises.
After all, how many just-layed-off employees will want to steal or damage company property to top off their recent loss of job with criminal charges and a criminal record?
From the outside it feels like a bit of paranoia on the part of US companies.
I might be missing something, this is just my opinion as an outsider.