Alternative to train current collectors (pantographs)
This blog says the wear lifetime is several months for the carbon "shoes" on the pantograph. Graphite carbon is itself a fairly good lubricant, so the friction is comparatively low. The system is incredibly simple and doesn't require too much fancy equipment per km of rail.

The problem with arcing is that it actually causes quite a lot of wear! So much so that it can be used as a machining technique: Electrical discharge machining. It also wastes a chunk of energy in the arc that goes to heating the air.

The "high frequency" Tesla coil approach would require an efficient means of generating high-frequency current at very high power levels (megawatts). While I don't think it's impossible, it feels like it would have high losses, and I'm not sure what level of radiated EMI it would produce given that it's the same architecture as an AM radio transmitter?