Cracking isn't always detrimental.

As for the use of iron, it has a lot of beneficial properties with regards to machinability and wear resistance (valve guides and seats).

Grey iron also has beneficial damping properties. It's also a lot easier to cast with cores, and with finer features, than steel.

I think it was a video for MTU medium size diesel engine they mentioned a cast steel block and showed using steel scrap in the mix. The reason I feel they only used cast iron is just like now, why they use a lot of aluminum for all the "junk" engines. Small lawn mower size up to the general automotive engines. Its all about the cost to manufacture, they don't give a rip if the parts crack years down the road.
Cast steel would be much easier to deal with as far as welding. It may add a bit more rejection during the casting process, again all about the costs.
Tugboat, yeah good old cracked D342 pistons, I have reused them many times, thems aluminum, and never had a problem with them.

Lol.

In the large engine market there are fabricated steel blocks but no cast steel. The MTU 8000 engine is quite large for a cast block but still uses nodular iron. The fabricated blocks can be repaired by welding. Cast blocks are done with stitching pins.

Have a look at this video, it has a very good section on the casting of the block for a MTU 8000 series engine. (I only have experience with the 2000 and 4000 series).

Even not so large engines crankcase-blocks are fabricated, EMD and OP Fairbanks Morse, at least they used to be. Now?
Here is the video.
https://www.youtube.com/watch?v=HlUWLCRZvLM
And at the 7:30 time, he calls it "steel", I doubt that is an iron casting.

https://www.google.com/url?sa=t&source=web&...

Thanks guys! So it looks like cost being the main reason beside more difficult to cast.

at that time they still didnt really know what they were doing with ci. today gray iron doesnt crack and is welded, especially at the foundry. before going to steel you would use some type of adi today.

Heavy duty automotive diesels use compacted graphite iron [CGI], stronger than grey iron, hence thinner walls = lighter.