The theory of weaker led on severance is:

1 - If you make it too hard to let people go, companies will be less willing to hire. (You’ve added a cost to the employee)

2 - If you make the cost of severance too high, it will kill companies that might otherwise have a chance to squeak through.

There are plenty of good arguments on the other side (companies offloading social costs to the govt, etc) but these two are consistent with economic theory on labor supply and demand.