why do you need credit card for trial period

I would really like to explore the power of Geni thoroughly before committing to a pro version.

However I don't understand why you need my credit card details for the trial period. isn't that being presumptive that signing on to a pro version is inevitable?

In the past I have lost money because of the Internet Provider being down in my locality just a day before the trial period closed. why should the onus of closing be on the user. you can use a time stamp to programatically log me out of the trial period 

this is what has been preventing me from trying out the rest of your capabilities.