Why aren't driving roads also illuminated from the ground up, like airport runway lights?

In ground lighting is more expensive and requires the light source to be able to be run over by all vehicles that use the road, including very heavy vehicles. Such lighting only acts a point source of light that illuminates a small area on the ground as most of the light goes out into space. Care would be need to ensure the in ground lighting did not produce glare that would blind drivers.

In most urban and heavily trafficked areas, overhead street lighting is used. The benefits of this is minimal glare for drivers, light goes downwards and illuminates an area on the ground, were the illumination is required.

In less trafficked regions, drivers can use the car's high beam lights.

I would think because airports are really well maintained while regular road lights get covered in dirt, sand, mud, debris, and snow. Also, vandalism is more difficult when the lights are higher up than when they are at ground level.

Functionally, it also makes sense for airport lights to point up since the planes are looking down. I don't think airport lights are meant to actually illuminate things on the runway either so they don't need to point at the ground.

Whereas for road lights it makes sense to point down since you are lighting the ground with a cone of light that gets larger the farther it goes. Upward facing roads light wouldn't have anything to reflect the light off of back towards the ground so it would take a lot more lights. Have you ever noticed upward pointing ceiling lights indoors? They often (always?) have a reflector so the light reflects back towards the ground. Just reflecting off the ceiling isn't enough sometimes. Compare this with outdoors lights where you're trying to light a much larger area and have nothing but a non-reflect, open sky above the light.