Obviously it all depends on the situation and the individual. I bolded the above as it's one (likely the main) use of life insurance, but there are others - debt elimination, creation of liquid wealth when it may be needed most, estate tax payoff if needed, leaving a legacy to a school/church/non-profit, special needs dependents, retirement/pension maximization (my latest two cases were concerning this), and others.
Here are just some thoughts - if you're 30 and you buy a 20 year term, you're covered to 50. Lets just say it's a 500k policy, you can get those really cheap if you're health. I ran a quick quote and a 30 year old male can get that 20 year term for $405 a year (obviously you can pay that monthly). After 20 years you've put away 8,100 in premiums - but now you're 50 and you said you needed coverage to age 70. Well, go buy another policy and hope you're still healthy enough at 50 to get a good rate (many are no longer). Even if you are, it's going to be 1,300-2,000 a year for a new 20 year term. Lets call it 1,500. Should you make it to age 70, that's another 30,000 in premiums - for a total of 38,100 in total premiums over the last 40 years and you're still with us at 70 - so you have no coverage going forward, and no equity (cash) accumulated.
Now lets say you have a twin brother who way back at age 30 bought a whole life policy for 500k. It was more expensive from the start, around 2,550 a year. Yeah, that sucks as it's ~2,000 more a year for the first 20 years, and ~1,000 more a year for the following 20. That's a total of 60k more in total premiums over that 40 years, which isn't chump change. You also have ~290k of cash in the policy. Yup, at that point you have put in 102k in premiums, and you have nearly 3x that in cash value (which you can access tax free) - and you've had coverage for the last 40 years, and you'll have coverage at age 71, 72....all the way up till you die. The cash value is totally liquid as well, and you can use it to pay the premiums should you have a cash flow issue. Life insurance can do quite a few things, especially if it's permanent, and building cash.