I believe long term disability insurance is a must for a safe personal financial plan. The risk of not being covered isn’t worth it. An office worker should have a very low risk of something happening that qualifies you for receiving benefits (even with fairly serious injuries for a hunter-gatherer or farmer they can earn a living).
That is actually the perfect situation for insurance. Insurance should be cheap when the risk is small. You want insurance for unlikely but very costly events. You don’t want insurance for likely and inexpensive events (paying the middle man just adds to the cost).
I believe, other than health insurance it is the most important insurance. For someone with dependents life insurance can be important too. And auto and homeowners insurance are also important. Insurance if an important part of a smart personal finance. It is wise to chose high deductibles (to reduce cost).
In many things I believe you can chose what you want to do and just deal with the results. Forgoing health or disability insurance I think don’t fall into that category. Just always have those coverages. I think doing without is just a bad idea.
When I would have had gaps in coverage from work, I have purchased disability insurance myself.
I am all in favor of saving money. About the only 2 things I don’t believe in saving money being very important are health and disability insurance. Get high deductible insurance in general (you should insure against small loses). And with disability insurance you can reduce the cost by having the insurance only start after 6 or 12 months (I chose 12). As you get close to retirement (say 5 years) the risk is much less, you only have so many earning years left. If you wanted to save some money at that point it might be ok if you have saved well for retirement and have a cushion (in case you have to retire 3 year early). Long term care insurance may well be wise to get (if you didn’t when it was cheaper and you were younger. Long term care insurance is really tricky and very tied to whatever our politicians decide not to do (or do) about the broken health care system we have in the USA. The cost also becomes higher as it is moving toward a likely event, instead of a unlikely event (as you age you are more frail).