Because God is truly glorious,
Psalms 115:1 Not to us, O Lord, not to us; but to thy name give glory. Psalms 115:2 For thy mercy, and for thy truth's sake: lest the Gentiles should say: Where is their God? Psalms 115:3 But our God is in heaven: he hath done all things whatsoever he would.
and idols are vanity,
Psalms 115:4 The idols of the Gentiles are silver and gold, the works of the hands of men. Psalms 115:5 They have mouths and speak not: they have eyes and see not. Psalms 115:6 They have ears and hear not: they have noses and smell not. Psalms 115:7 They have hands and feel not: they have feet and walk not: neither shall they cry out through their throat. Psalms 115:8 Let them that make them become like unto them: and all such as trust in them.
he exhorteth to confidence in God.
Psalms 115:9 The house of Israel hath hoped in the Lord: he is their helper and their protector. Psalms 115:10 The house of Aaron hath hoped in the Lord: he is their helper and their protector. Psalms 115:11 They that fear the Lord have hoped in the Lord: he is their helper and their protector.
God is to be praised for his blessings.
Psalms 115:12 The Lord hath been mindful of us, and hath blessed us. He hath blessed the house of Israel: he hath blessed the house of Aaron. Psalms 115:13 He hath blessed all that fear the Lord, both little and great. Psalms 115:14 May the Lord add blessings upon you: upon you, and upon your children. Psalms 115:15 Blessed be you of the Lord, who made heaven and earth. Psalms 115:16 The heaven of heaven is the Lord's: but the earth he has given to the children of men. Psalms 115:17 The dead shall not praise thee, O Lord: nor any of them that go down to hell. Psalms 115:18 But we that live bless the Lord: from this time now and for ever.