You'd think that after Cell beats Piccolo on the islands he would've tried absorbing him again, but he just blasts him and chucks him into the water. Cell himself said that the Saiyan genes in him made want to continuously seek strength, so it doesn't feel like it makes sense for Cell to waste a powerful life force like that even if he was stronger. It's not like he had given up on absorbing people either since he immediately tries absorbing #16 after he gets sucker punched by him and before he realizes how strong #16 is.