Why do PTC(pay to click/paid To Click) sites give the viewers money? What is the benefit for them?

[Jake]

Some, not all may be ripping off business that are paying for advertisements, some pay per click advertisements cost a small business a few dollars each time it is clicked, web site operators hosting these ads get about 50% of the advertising fee, paying people like you a couple of cents to pretend to be an interested shopper is probably a violation of the law, and really hurts that business paying for the ads.
In other cases the PTC biz had legit paid advertisers who may be hoping to entice the paid clickers to do some other work at home business.

This is a very shady business, commonly ripping off the clickers ans well as advertisers, there are certainly better ways to spend your time, one can earn a few dollars writing articles for web sites, if old enough freelance marketplaces like odesk.com, elance.com would be a step up.