Many don't like dealing with banks, or would write too few checks to make it worth paying the fees. The banks, for their part, generally don't welcome people with limited means. They can apply for an ETA at a participating bank. They could then receive their benefits electronically, as most of the middle classes do. Even people with poor credit can open one of these accounts.
ETAs save the government money because it's cheaper to pay electronically than to mail paper checks.
As for the unbanked, they should find ETAs cheaper than check-cashing centers. But ETAs only are for cash withdrawals. They may disappoint people who would like to pay bills by check. About 600 institutions with 5,300 locations have agreed to provide them. Still, ETAs will be only slightly profitable.