Because what caused you to choose an apple over a pear? Your genes and environment dictate your wants and your desires, too. Why did you choose that example, rather than apples over oranges? Because that wasn't the example that arose in your brain, beyond your control. If I ask you to think of a rugby player, several of them will pop into consciousness. Were you free choose which players sprung to mind? No. My question simply triggered you to think of one or several different players.
To be honest it's interesting theoretically but sorry I will again reveal myself as a Bible bound brainwashed extremist when I say that I believe in free will because God has given it to me