You pay for peace of mind that little Johnny doesn't download some crazy amount by accident. Now you don't have to monitor family usage so that makes things easier as well.
the price was competitive too. other ISPs charged $70 per month, and had a limit of 50gb (that was 15 years ago) my ISP charged $20 as base fee and $1 per gb of usage. if i used less than 50gb, i saved money, if i used more then i could...