In an episode of Today I Found Out, Simon Whistler explains the reasons drive through ATMs still use braille. The primary reason is that they are required by law, despite objections by the American Bankers Association, but there are also a number of situations where a person with visual impairments could be using the machines.
Mainly, it is because it is required by law, thanks to the ADA Accessibility Guidelines for Buildings and Facilities. There are certain exceptions, in terms of these requirements, when it comes to drive-up ATMs vs. walk up ATMs, such as the differing requirements on the “Reach Ranges” in section 4.34.3. However, being able to get rid of the Braille is not one of these exceptions, despite initial protests from the American Banker’s Association who argued that any visually impaired person could simply get the driver to help. The committee in charge of coming up with these standards rejected this argument because it would no longer allow a visually impaired person to use the ATM independently.