Four out of 10 American households with children under 18 say they would have immediate difficulty paying for everyday expenses if the primary breadwinner died today, according to research by LIMRA, a firm that tracks the life insurance industry.

Another three in 10 would have trouble keeping pace with expenses after several months, LIMRA found in the 2010 "Trends in Life Insurance Ownership" study.

Sobering statistics like those point to the need for life insurance.

Yet individual life insurance ownership is at a 50-year low, according to the LIMRA trends study. Only 44 percent of households have individual coverage, and 30 percent have no life insurance at all, up from 22 percent in 2004.

Why aren't people buying?

Here are four of the most common excuses:

1. I'll do it tomorrow.

According to "The 2011 Insurance Barometer Study" by the Life and Health Insurance Foundation for Education and LIMRA, 86 percent of consumers say most people need life insurance. But just 63 percent of all study respondents have purchased their own coverage. Many people put it off because they're confused about what type of coverage to buy, and how much.

But what would happen if you died without ever having purchased life insurance? Neglecting to do your homework today could spell financial disaster for your family tomorrow.

2. It's too expensive.

When money is tight, families understandably don't want to add another bill to the stack. But insurance rates for term life are only a fraction of those for permanent insurance, such as whole life or universal life.

Term life insurance does not have a cash savings account and provides coverage only if the insured dies within the term. You choose a term, such as 25 years, to cover the critical period when your family is most financially vulnerable--while the kids are growing up and there is a mortgage to pay, for instance.

3. I already have group life insurance through my job.

Employer-sponsored group life insurance generally lasts as long as the job. If you quit or are laid off, you no longer are covered. Group life policies are also for relatively small amounts. They may not provide enough coverage to meet all your family's needs.

4. I don't know any life insurance agents.

Most insurance companies that sell other types of insurance, such as car insurance and home insurance, also sell life insurance. But only 48 percent of consumers are aware they can purchase life insurance from these multi-line companies, according to LIMRA's "The Insurance Cross-Purchase Survey," released in November 2011. A good resource for guidance might be in your own back yard--your home or car insurance agent.

You can also find a wealth of information online about the basics. The LIFE Foundation website provides information about types of coverage and choosing how much insurance to buy.