I wish this were more common. For some reason, employees are expected to give employers two weeks or more of notice when they quit, while employers are expected to terminate employees with 0 seconds of notice.
I think there's a fear from the employers that the terminated employees will do something to fuck over the company because they're bitter, either by copying and distributing proprietary stuff, or even just posting a message shit-talking the leadership. Everyone knows that being fired or laid off sucks and passions can run high, so there is a perceived incentive that bitter employees will cause some damage.
I honestly don't think most people would do that, but I think there's a worry that "one bad actor is enough". Consequently, when I've been laid off in the past, usually my access to the computer (Slack, company email, and the computer itself) is cut off about a minute after I get the bad news.
That said, usually I get severance when I've been laid off, which is admittedly a small consolation, but a consolation all the same.