So if we take my wife's grandma's example, often by the time you need LTC, the insurance benefit you purchased is only a fraction of what the nursing home actually costs. So she bought a policy with a benefit of $1k/month in the 80s, and needed nursing home care in 2013. Her nursing home cost $6500/month, so while it helped, she paid premiums for over 25 years for a policy that covered 15% of her costs. She still had to make up the rest out of income, assets, and Medicaid.
I don't fully understand the details of the insurance product you are being offered. Is there a cash benefit upon death if she doesn't use the LTC portion? Does she pay the $75k now or over a period of years? The answers change the math slightly, but the story is still the same.
In your mom's case, let's assume she needs LTC in 2035 and nursing home costs grow at 4% a year (which is a fairly conservative estimate) from the $6800/month U.S. average. Let's also assume her assets do in fact grow at 5% a year. Also assume she spends none of her assets on other things, even though it is unlikely that she won't need assets for anything else.
Her assets today without insurance are $200k, and with the insurance purchase drop to $125k.
In 2035 a nursing home costs $13,245/month. She still has $1600/month in income and insurance would give her $3300 in benefits, so the net cost of a nursing home after her income is used up is $11,645 without insurance and $8,345 with insurance.
In 2035 her assets are $467,902 without insurance and $292,429 with insurance.
Without insurance, she can pay for 40 months of a nursing home with her assets and income. ($467,902/$11,645)
With insurance, she can pay for 35 months of nursing home care before her assets are fully depleted ($292,429/$8,345). She then has another 37 months of a $3,300 benefit, but she'd need Medicaid anyway because her income plus benefit doesn't pay for the full cost of the nursing home.
My back of the envelope math is a little rough around the edges, but it tells the basic story. This scenario assumes your mom has a 100% chance of needing nursing home care, which is not the case. The math is even more in favor of no insurance if she ends up not needing a nursing home, or she only needs a short nursing home stay. The average length of stay in a nursing home is 2 years, 3 months.
Basically, these insurance salesmen prey on your fear of the unknown and the extreme costliness of healthcare to convince you that you need insurance, when actually, LTC is one of the things that most people can self insure for. You have Medicaid as a backstop if things go dramatically off the rails (all assets get spent, or a very long length of stay) but most people can just spend down their own assets to pay for care.
Having been through this with a family member, I can say that the money she paid for LTC insurance would have been much better spent paying for things she needed as she got older. Medicare doesn't cover hearing aids and she was so stressed out about covering the cost on her fixed income, while still having to pay the LTC insurance premium. In the end, the LTC insurance benefit was negligible in her care decisions.