People with "disabilities" often have to buy off the shelf equipment made for the mass population, and then adapt it for their needs since most products aren't designed with them in mind.
People who are blind don't necessarily lack vision - that's why the bobbled paving slabs at the edge of crossings and train platforms are bright yellow. [1] Admittedly the LED wouldn't do anything a tactile or audible click wouldn't do here, but a blind user most likely would be able to see that an LED was lit somewhere.
aside from it being embossed tape added after market:
blind covers a lot of ground. the ability to discern a red led against a black background when you're a couple feet away is well within the realm of blind