Because the 158gr LSWCHP works, even in a 2" snub. If it fails to expand, it's flat meplate is crushing tissue along it's path. It is not the best for barrier penetration & probably the greatest reason for the switch to lighter JHP today. In 38sp+P, even in a 4" bbl you only get about 950fps, leading is not an issue. In a 6" you might break 1000fps, still not a leading issue.
I have a couple 357mag snubs. If I carried either,it would be with some vintage era FBI loads. Easy to shoot & get good hits at speed. The bullet will do just fine as long as you arent shooting thru hard barriers.

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NRA Cert. Inst. IDPA CSO