Infantry Anti-Tank Mines (thrown), HEAT rounds, APHE rounds, Shaped Charged Weapons (Panzerfaust, Panzerschrek, Bazooka, PIAT ect), ATR rounds were all being upgraded or newly developed by 1942. Even a Molotov Cocktail from certain angles, could be thwarted by Shurzen to a degree.
There was a wide variety of threats to AFVs, certainly not just limited to domestically produced ATRs.
The "original purpose" of Shurzen may have been Russian ATRs, it was certainly not kept on their AFVs, <solely as a defense against just Russian ATRs>.
The Germans did not remove Shurzen when deployed to the West, one can draw the obvious conclusion as to why.