Why in Islam, leaving it is punishable by death?

 Why in Islam, leaving it is punishable by death? 

Alhamdulillah, islam is a religion that is based on truth and accepting it and rejecting brings fitnah. 

Just like the jews of Medina said, 

Aal-e-Imran 3:72

وَقَالَت طَّآئِفَةٌ مِّنْ أَهْلِ ٱلْكِتَٰبِ ءَامِنُوا۟ بِٱلَّذِىٓ أُنزِلَ عَلَى ٱلَّذِينَ ءَامَنُوا۟ وَجْهَ ٱلنَّهَارِ وَٱكْفُرُوٓا۟ ءَاخِرَهُۥ لَعَلَّهُمْ يَرْجِعُونَ 

And a faction of the People of the Scripture say [to each other], "Believe in that which was revealed to the believers at the beginning of the day and reject it at its end that perhaps they will return [i.e., abandon their religion],

So this is what the hypocrites use to do, to destroy the faith of people and the deen so Allah brought such ruling that if one does accept the deen and neglect it opens way for fitnah and people to play with Islam. 

Just like if one loves a country and show betrayal of the country is accuse of treason and jailed or sentence to death in some countries or as a spy. Why if same rulings and actions are applied in Islam. 

But some scholars say like imam shafi', 

The person is given time like three days to change his mind or else he will be killed for apostasy and asked to know the reason why he revert his deen. 

May Allah s.w.t safeguard us and our eeman. Aamin