It's all about the carbon content in the steel.
Spikes are relatively easy . . heat 'em & beat 'em.
Cable, due to the higher carbon content makes into some very nice knives but requires forge welding like pattern welded/damascus steel. Forge welding is a whole 'nother learning process entirely.
Because it's laminated there's lot of opportunities for weld failures ie. cold shuts, incomplete welds etc. It's quite a bit more labor intensive to make a billet before the grinding/ knife making even begins.
So far, I have about 6 feet of cable attempts in the trash.
Larry