The question "Who still believes in God?" is grammatically incorrect due to it being intellectually dishonest.
"Who..." - "Of all living humans..." This is grammatically acceptable as well as intellectually honest.
"Still..." - "After examining all the evidence..." This is grammatically acceptable as well as intellectually honest.
"Believes..." - "Holds an opinion that is not necessarily based on facts..." This is grammatically acceptable as well as intellectually honest.
"In..." - A better choice of words would be "the existence or past existence."
"God" - Here is the biggest problem. "God" is implied to be the YHWY, Jesus, Allah of the Judeo-Christian-Islamic faiths. To accept the existence of one of these 3 you must accept the existence of the gods of all faiths exist. The factual evidence used in an attempt to prove the existence of "God" also proves the existence of all "gods".
So a the better way to word the questions "Why still believe in God?" would be -
"Who among all of us, after examining all the evidence, holds an opinion that is not necessarily fact based that there exists or there has been in existence the gods of human religion?"