Regarding the "How am I charged" information: just curious, why did you decide to go with that setup (an "piggy bank" that you fill and then are deducted from o

Regarding the "How am I charged" information: just curious, why did you decide to go with that setup (an "piggy bank" that you fill and then are deducted from one day at a time at a set rate) instead of the more standard "We charge you $30 monthly at the beginning of the month" practice? Easier for you on your end? Or do you think the customer gains a benefit from it? Just curious (Note: I'm not someone who's thinking about buying this and held back by this practice, just a curious bystander).