No it doesn't - the reason is that to give you 'free' 3G, there must be some sort of incentive in it for the company. Amazon give free 3G as you are buying books from them. You can't use this wifi for watching YouTube etc.
If you are using a tablet (like the Galaxy) since it does a lot more than just let you read books, you may well use a lot of data. Since Samsung aren't getting any more money out of you, there is little point in giving you 'free' 3G.
Therefore most tablets are also sold with data plans - ranging from £10 a month and upwards - so that (like a mobile) you can connect to a website whenever you want.
Hope this helps