Many times the offers are a thinly-veiled attempt to get rid of their older (more expensive) employees. People nearing retirement age are most likely to have many years of service, making a severance package that pays per tenure especially appealing. And there’s the threat of layoffs if you don’t accept the offer. If you’re in your 50s or 60s it’s hard to get a new job regardless of how qualified you are, so this makes gambling on your continued employment risky.
My mother went through this exact exercise two years ago. Management was clear that, if not enough employees took the buyout, they would start layoffs with less generous terms. From previous rounds of layoffs she knew older employees were the first to go, so she took the buyout and got 52 weeks paid severance.
The day she resigned, she received a termination letter offering only 40 weeks. Fortunately the company stood by the more generous offer. But it took her the better part of a year to get a new job, and it pays much less than the one she invested 30+ years in. She’s from a generation when you worked at a single company for life, but companies don’t operate like that any more.