Read this for yourself:
2:217-Whoever of you recants and dies and unbeliever,....shall be the tenants of Fire,wherein they shall abide forever.
NOTE:This verse keeps Muslims trapped in Islam for fear of hell.
4:89-If they desert you,seize them and put them death wherever you find them.
NOTE:Fear of death is why only few people leave Islam.
16:106-Those who deny Allah after possessing Islam and open their bosoms to unbelief shall incur the wrath of Allah,grievous punishment awaits them.
NOTE:This means death to those who leave Islam.
47:25,27-Those who turn back(from Islam) angels shall gather them,smiting their faces and their backs.
63:3,4-They believed and then renounced their faith...they are the enemy. Guard yourself against them. Allah confound them..!!