I believe that Jesus explains why:
2 Timothy 3:1-5 (NKJ) 1 But know this, that in the last days perilous times will come: 2 For men will be lovers of themselves, lovers of money, boasters, proud, blasphemers, disobedient to parents, unthankful, unholy, 3 unloving, unforgiving, slanderers, without self-control, brutal, despisers of good, 4 traitors, headstrong, haughty, lovers of pleasure rather than lovers of God, 5 having a form of godliness but denying its power. And from such people turn away!
and Matthew 24:3-12 ... And because lawlessness will abound, the love of many will grow cold.
We have become lovers of self.
Solution: repent (recognize), seek God, ask the Holy Spirit for renewed love. Walk in the light, read the Word.
But I believe not many want to do that ...