Some insurers may exclude people from cover in certain circumstances if they are deemed to present too great a risk.
Also, an insurer may list other situations in which it might not pay out, for example if the insured party was in some way culpable for their own death.
The following may be reasons for an insurer to turn an applicant down for cover:

If you work in a job that is considered “high risk”: this could apply to certain construction or oil industry workers, as well as members of the armed forces.

If you regularly engage in risky pastimes, such as parachuting, mountaineering or motor sports.

If you have a history of serious health problems, such as high blood pressure, cancer or diabetes.

If there are lifestyle issues that make you a greater risk to insure, such as if you are a heavy smoker or seriously overweight.

You should bear in mind that not all insurers approach these issues in the same way, and with a great deal of competition in the industry at the moment, it should still be possible to find cover at a decent price even if one of these factors applies to you.