Firstly many people create dating sites because they know it creates interest and their real motives may only be to get you on their site for some other reason, usually so they can get many visits to their site to make it easier to sell advertising on that site. The main reason some sites get you interested is to divert your attention to something else on their site. If the site is totally free you may be bombarded with email or advertising. Some people who have dating sites have had no experience in the introduction agency business and may not understand what they are doing. Most Internet introduction services do not verify the identity of their clients.
Many sites are unsafe.
Some sites publish you email address which is an open invitation for harrassment for you. Other sites cater for married people, also there are sites that try to cater for every possibility. Many sites do not verify the identity of their clients. Most sites are strictly internet based and many make you do all the work searching. While this may retain your interest, you are unlikely to make the right choice and many people may have withdrawn from these sites or be very old listings.