This would improve customer service, make it easier for moms/dads with kids to use the USPS, and allow for them to remain competitive.
Currently parents with kids, will have to unseat their kids, haul them into the PO, just for a five minute transaction – or to check their PO Box. I would be willing to pay for this service thru increased postage rates or a drive-thru surcharge. Allow me to drive through, show ID and get my mail from my PO Box, mail letters, or pick up mail.
Major transactions and packages would still have to go to the counter.