it was from the era when every attempt was made to downplay comic book origins and any superhero had to wear black leather instead of a colorful costume.
Blade was never meant to be a traditional superhero. He was spun off by Marvel from their Tomb of Dracula comic. This was basically a comic based on the premise that Dracula was resurrected while a team led by a descendant of Van Helsing tried to destroy him. Somewhere along the way, they crossed paths with Blade, who had the same mission. Blade was then spun off into his own comic. As I recall, he wore a long coat and not a superhero costume.