First of all, that’s irrelevant, and second, it’s not the whole truth. There were white raiding excursions that would capture Africans.
Diseases, hostile native people, bad maps or NO maps, extreme weather, language barriers, challenging terrain, etc. made travel into the interior out of the question.
White slavers established strongholds on the coasts, where native chiefs (many of whom were Muslim) brought masses of their unfortunate 'brothers' to enslavement. The chief who brought their brothers out of the interior held MANY slaves of their own and always had. It was a long standing, well organized and lucrative business for them.
All the way up to the very early 20th century, white people could hardly expect to survive travel into the interior.