Maybe the management and culture changed such that it ceased being a pleasant place to work?
For about the first 40 years of my working life I, and most of my colleagues, were really hoping that we would be allowed to continue working after retirement. Management was relaxed as long as the job was done. We worked hard and long hours when needed without any pressure from above. When the work was light we relaxed. In the early 90s there were changes at the top. Gradually the culture changed. Management became increasingly demanding and reluctant to accept that there might be genuine reasons for someone not wanting to work evenings/night or over the weekend. There were threats, in the limit, of the sack. It stopped being a pleasant place to work.
When I was 62 an "early retirement" offer (voluntary redundancy) was made to all over 60s. Many of us jumped at the opportunity. 15 years later I am still in touch with many of them and we all consider it was the best thing to have done, yet had the culture been that of the 80s or earlier I doubt many would have taken it up.