Why do I need to apply?  I already know how much life insurance I want.

Yes, you know how much coverage you want, but the insurer doesn't know whether it wants to sell that much coverage to you—or even if it wants to sell you any life insurance at all.

If the insurer does decide to sell you life insurance, it's going to require some time to determine at what rate it can afford to extend you coverage.  It usually requires 4–6 weeks for the underwriters at the insurance company to request and review your medical history, family history, and anything else it needs to determine what your rate class should be.

If you are in good health, you can obtain temporary coverage to protect you while you wait for the insurer to complete its underwriting.  This is known as "binding" coverage.

After it determines your rate class, the insurer calculates your life insurance rate by factoring in your age, your sex, and how much coverage you want.  Then it makes you an offer, and the ball's back in your court.  Are you going to accept the offer?

Actually, there is an alternative to the lengthy application process.  Guaranteed issue life insurance does require you to fill out an application, but it involves no medical inquiry and no underwriting.  You can have your policy in force in a matter of minutes.