Scenario #1: You are 40, FI and plan to ER one year from now. You cancel your disability insurance. The very next day, you are severely injured in an accident. You require hospital care, rehabilitation for months, and ultimately need a wheelchair, a hospital bed, catheters and other medical supplies, and physiotherapy and home nursing care indefinitely. You can no longer work, and you have a decreased quality of life. The cost not covered by your health insurance will amount to millions over the rest of your life, which is estimated at 20 years. You have no legal recourse because the accident was your fault. Your NW is no longer sufficient. You end up destitute and your kids get no inheritance.
Scenario #2: You are 40, FI and plan to ER one year from now. You decide (as I did) to keep your disability insurance for the next six months, knowing that the policy has a 180 day waiting period. The very next day, you are severely injured in an accident. You require hospital care, rehabilitation for months, and ultimately need a wheelchair, a hospital bed, braces, catheters and other medical supplies, and physiotherapy and home nursing care indefinitely. You can no longer work, and you have a decreased quality of life. The cost not covered by your health insurance will amount to millions over the rest of your life, which is estimated at 20 years. You have no legal recourse because the accident was your fault. Your disability insurance covers these expenses. Your NW is sufficient to cover other living expenses. You remain FI and leave a financial legacy.
My point is that disability can be very, very costly over time. Permanent disability lasts for the rest of your life, not just while you are working. Just because you have a SWR worked out while you are healthy doesn't mean that that SWR will cover all the expenses you may have if you become severely disabled. It seems to me that it would be a shame not to insure against such a catastrophe while you can. The cost of disability insurance reflects the fact that disability is not as rare as one might think, and when it occurs, it is expensive.
Different people approach risk management in different ways and there is a gender difference. The OP's viewpoint is understandable, as is his DW's.