You’re right there’s not just 1 pregnancy site out there but all the others i have found that offer a personalised charting service charge a subscription fee, so yes it is a freebie :)

Ok where would you like me to start? Firstly the example site you gave is a generic ovulation chart and assumes every cycle is the same and gives you fertile days based only on how long your cycle is etc. With Pre Conceptions users enter data for each day throughout the month and all info is stored in the database. The ovulation and fertile times are calculated using that personal data and is different for each cycle and each woman. (hence the term personalised). Not only do they have their own personalised charts but they can post in the forums, have their own personal blog to keep track of their pregnancy or trying to conceive journey and also have photo storage to keep pics of ultrasounds etc within their own personal photo album.
Try this site http://www.fertilityfriend.com this is a perfect example of one of the most popular sites for trying to conceive, they have an option to chart for free but you cannot access the forums or certain features unless you are a paying member. Pre Conceptions offers everything they offer only for no charge at all. I make no money off this site and have no ill intentions. I am trying to help women who are having trouble conceiving as i am going through the same issues and it doesn’t feel right to me to get rich off their troubles. I have created a place where they can get answers, support, a personalised service and hopefully the baby they always wanted and not have to worry about paying a cent for it. I obviously understand where you’re coming from but how is it just plain out right advertising if the site is totally free and i do not make a cent off it?