1 Peter 3:15 and 2 Corinthians 13:5

[15] but in your hearts honor Christ the Lord as holy, always being prepared to make a defense to anyone who asks you for a reason for the hope that is in you; yet do it with gentleness and respect,

This verse says that we should always be prepared to defend why we believe in Christ and why we follow him, yet many Christians today refuse this claiming it's personal and is just between them and God. Why do we not do this? Some can be because they don't really know why they believe. Some because they have hardened their hearts believing only some deserve salvation. Some because they are fearful of the repercussions when the world rejects them. And so on. Why don't we teach more people to defend their faith?

I understand that only God and the person can truly know, which is why we are also called to examine ourselves regularly to see if we are still in the faith. 2 Corinthians 13:5 ESV

[5] Examine yourselves, to see whether you are in the faith. Test yourselves. Or do you not realize this about yourselves, that Jesus Christ is in you?—unless indeed you fail to meet the test!

Why would we have to examine ourselves to see if we are still in the faith if we can't lose it?