Train inspections are far less intrusive. Wheel wear can be measured with calipers while standing beside the train. Software tests are physically null, except for alarms sounding. Brakeline tests can be verified without adding gauges; in many cases the braking mechanisms are externally observable.

Plane controls systems all live behind thin, deformable metal or plastic covers.

Trains aren't perfect, obv, but most train accidents reduce to "A human on the tracks fucked up". Drivers trying to maintain schedules by speeding, or vehicles or humans standing on rails where they had no business being (dodging crossing guards, suicide, etc).