Well, I'm not saying running ftp to serve html is better. All I'm saying is that it can sometimes be the only supported option, or viable option. And there are major differences. Webserver access permissions vs. ftp server permissions for example?
What I'm saying is: is there a meaningful difference? Both need to bind to a port that is privileged and read files from the served directory. There is no difference between a ftpserver and a webserver from a permissions/privilege perspective.