Back in the 80s when the symbiote was introduced, it would take Peter's body out at night to fight crime as Peter accidentally taught it to do. When Peter went to Reed Richards to find out why he so tired everyday, and found out his suit was alive, he promptly abandoned it. The symbiote bonded to Eddie Brock, and Brock's hate for Spidey tainted the Symbiote. Current writers have been trying very hard to make the Symbiote seem really evil like it was sucking out Peter's soul. To me the symbiote's treatment was unfair. If it had stayed bonded to Peter, it would probably take the form of a hot girl since Pete's always surrounded by hot girls (Mary Jane, Gwen Stacey, Liz Allen, Betty Brant, Carlie Cooper, Felicia Hardy, Silver Sable).