Why do you think my dad left? :(?

iwas in my moms stomach before he left and they separated because he cheated, so after iwas born he started visiting me and then he left when iwas about 5 supposibly according to my mom because he was mad that she put child support on him and that he would buy me presents a little after because he wanted it gone then my mom said she's not guna take it off and then he never came back I haven't seen him since and now I'm 18? So why did he leave :'(