A reason is to “reward” us greatly for it as the example verses below show:

(i) A Reward on Earth = “Great Peace” & “our righteous deeds have more value because they are done more accurately in God’s Will”

“If only you had paid attention to My commands. Then your peace would have been like a river, and your righteousness like the waves of the sea.” (Isaiah 48:18, HCSB)

(ii) A Reward in the Heavens = “become greater in His Kingdom”

“Whoever then shall break one of the least of these commandments and shall teach others the same, he will be called least in the kingdom of the heavens; but whoever shall keep and shall teach them, he will be called great in the kingdom of the heavens.” – Lord Jesus Christ (Matthew 5:19, BLB)

Conclusion

God only intends Good when He requires us to “obey” His Commands (John 14:15, 1 John 5:3).

It is not love with conditions but rewards with conditions (Romans 2:6, Revelation 22:12). Salvation itself is a Free Gift of His Love as it is written (Titus 3:5, Ephesians 2:8).

However to receive Salvation we must first believe (John 5:24) & the rest are Judged first to receive the rewards of their evil deeds first in Hell (up to the age according to one’s own sins, Matthew 25:46, Matthew 5:26, Revelation 20:15) before they are reconciled or saved, even so by fire (James 2:13, 1 Peter 4:5 – 6, 1 Corinthians 3:15, 1 Timothy 2:4, 1 Timothy 4:10, Colossians 1:20).