Bresenham's algorithm as originally designed lends itself well to implementation in hardware, where you don't want a more complex implementation than necessary, so I'd say it still matters…if GPUs bother to implement GL_LINES in hardware anymore.
(I don't know if GPUs bother with it any longer. The OpenGL spec allows but does not mandate a Bresenham-based implementation, so tessellating into triangles is theoretically an option if they can make the diamond exit rule work. Games rarely use lines, but it wouldn't surprise me if they keep the hardware around for CAD software or whatever.)
Nvidia's Quadro GPU offerings still have 'proper' GL_LINES hardware support for CAD. I'm not sure if they still use Bresenham under the skin though. But most of the consumer GPU offerings just resort to tessellation into triangles AFAIK.
Though they remain in Vulkan as an optional feature, supported by all the desktop GPUs - so they're aren't going away anytime soon.
Of course, how much of that is driver fakery and how much is actual hardware support can be debated, but there's surely some hardware support, otherwise it wouldn't be exposed in Vulkan which is supposed to be a thin layer.
are you sure they are actually supported in modern GPUs . if you enable the core profile instead of the compatibility profile you get no thick lines. Whether those thick lines are gpu lines or software lines I don't know but usually when things are pulled out of GL it's becasue the are not actually supported in the hardware.
(I don't know if GPUs bother with it any longer. The OpenGL spec allows but does not mandate a Bresenham-based implementation, so tessellating into triangles is theoretically an option if they can make the diamond exit rule work. Games rarely use lines, but it wouldn't surprise me if they keep the hardware around for CAD software or whatever.)