They don't.
If you want to pay for one it costs about ten bucks a year: https://www.gandi.net/ssl/grid
If instead you want a free cert: http://www.startssl.com/
If you want to pay for one it costs about ten bucks a year: https://www.gandi.net/ssl/grid
If instead you want a free cert: http://www.startssl.com/
Also worth noticing is that SSL comes free for one year with domains bought at Gandi.
The more expensive certificates offer insurance, but if you read the small print you'll see that it isn't worth much.