Steel frames are only easy to repair if they're lugged, i.e. the tubes are brazed into lug sockets. This was once a common method of hand building frames, but it's now rare and expensive. See https://en.wikipedia.org/wiki/Lugged_steel_frame_constructio...
Compared to aluminum frames, all steel frames are more easily repaired. They can be welded without special equipment, put back in shape when slightly bent etc. They also fail less catastrophic - if an aluminum frame or fork receives even a slight bend in a dooring accident it needs replacing since it may just break clean though at the next inconvenient occasion (like hitting a slight bump downhill with high speed)