I'm sure the FAA would require the airlines to change them every 6mo. and the batteries would have to cost at least 5 times as much, because to go on an airliner, they'd have to be "FAA Certified".

30 years ago I was flying a small twin engine turboprop, about an 8 passenger size. One of the landing lights burned out so we flew with only one for quite a while. When I asked why not replace it, the mechanic told me a new one would cost $168.

This light bulb was about the same size you would use on a car, which at the time cost about $5...but it wouldn't be FAA Approved.