Some US banks charge "maintenance fees" if an account doesn't have a high enough balance, so he may have needed to wait for a large reserve to build up before using his debit card for daily purchases.
e.g. Wells Fargo currently requires a minimum $1500 daily balance (or direct deposits coming in, or mortgage payment going out- neither of which are applicable here) otherwise they charge $10/month in fees. Add to this the "creative accounting" some banks use to settle debits from day-to-day, and other nuances of ACH (no fraud protection, 5 days to dispute transactions, etc.) that make payment by check or debit card non-trivial for the inexperienced.
e.g. Wells Fargo currently requires a minimum $1500 daily balance (or direct deposits coming in, or mortgage payment going out- neither of which are applicable here) otherwise they charge $10/month in fees. Add to this the "creative accounting" some banks use to settle debits from day-to-day, and other nuances of ACH (no fraud protection, 5 days to dispute transactions, etc.) that make payment by check or debit card non-trivial for the inexperienced.