why? google and facebook are a distribution channel for people search. just google the name of you mother, grandmother, father in law, anyone not in the nerd, hacker, geeks segment and show what turns up (note: on the resulting pages, turn off your ad-block)

in non US countries the business model is mostly ads (from the sh*tload of pageviews), in the US the business model is mostly affiliate (delivering traffic to the thousands premium "criminal record / financial record background check" companies)

People don't always use their legal name on facebook and not everyone has enough online presence to show up on google. Peoplesearch pulls data from many sources e.g. your electric/water/broadband company.