Credit cards can be very useful, provided you pay off your outstanding balance at the end of each month. If you do not, the debt can pile up, and will be sticking with you for a very long time. Credit is a tool - it lubricates the economy. Without it, production would grind to a halt. However, it is very important that creditors lend only as much as debtors can afford to repay.
If we think of Debian as a gift economy, it is the community doing the lending, and ITPs and ITAs are a temporary extension of kudos to the potential maintainer.
Anyway, the point of this analogy is to note that while my financial overdraft is currently nonexistent, my debt to Debian needs to be repaid with interest.