There are insurance plan that one only needs to pay 5, 8 or 10 years, but the policy only matured in 15,20,25 years one.
There is single premium policy as well, pay once, but the policy run or only mature in 5 years or 8 years time.

End of paying premium /= policy mature.

Insurance policy and insurance company never cheat.

The probable reason may be due to

1. Policy owner doesn't understand clearly and fully about the policy itself, how it works, coverage, any riders etc.
Sometimes, policy owner may not aware the nature of the policy as well.

2. Insurance agent did not explain thoroughly and properly that lead to (1) above occurring.