knitted
been skydiving
played in a local sports league
either don't seem worth the time, effort and other investment vs other new experiences that could be had for less time, effort, expense, risk, etc.
A poster above hit a key point: responsibility. I'll extend it with: children. At some point, if you have children you care about, helping them get the most out of life, both while you are here and after you are gone, takes precedent. Instead of running a bucket list check-sheet for yourself, the real challenge is ensuring that your children can do the things they want to do in their lives.