See the NCR specification: Choose dual banknote export modules (types 6632 and 6634), up to 20,000 banknote capacity, longer service hours, and higher operating rates.
General ATM only comes with a cash-out module, standard. The capacity of up to 12,000 banknotes is enough for use. Normal ATM machines will not hold more than 6,000 banknotes, and 100 are 600,000, which is enough.
NCR is just doing this to increase service time and service speed. To be honest, for most bank outlets, this feature is a tasteless, full-featured chicken.