It is better not to count on severance package. That way, if it happens - great, and if not - it's easier if you weren't counting on it. Just saying.
However, hypothetically speaking, it is not clear to me how the company can get away with not paying severance pay to laid of employees........ although nothing would surprise me anymore.
True. No company has to offer severance pay. Companies offer severance only as a good will gesture to ease the financial burden of the employees losing their jobs.
Nothing to get away with, really. There is no legal requirement for any company in the US to pay severance. Period. The only way you'd possibly have a case is if you were in the same layoff, and you didn't get a payout when others with the same role and same years of service did get one. Other than that, they have to pay you for your time worked, and for any already accrued but unused vacation time. Period.