For his own peace of mind. There's a list of rules that most "smart" men adhere to when foreign dating and asking women to chat via their personal messaging apps is the first on the list. There are scammers on this site and they usually won't want to use Viber, what's app etc... and they definitely won't video chat. If after a week or two, a woman doesn't want to leave the site to chat, I will stop contact. If you want a man to trust you, ask to leave the site and video chat.