That's like saying, "If we speak english, why do people still speak german?". Humans are primates, and we share ancestors with primates like the chimpanzee, bonobo, etc. To ask a question of the form ‘If Species X evolved from Species Y, how come Species Y is still around?’ is to misunderstand how evolution works. Entire species do not evolve into new species; new species tend to evolve as isolated offshoots of existing (parent) species. Most of the info from here: http://friendsofdarwin.com/misc/faq/why-still-monkeys/