it used to be so that in order for a product to be called "dondurma" (ice cream) it had to have salep in it. all other regular ice cream had to be sold under the name "buz" (ice).
On the West Coast (Izmir, Dikili, Cesme, Bodrum) it is custom. It is sometimes called Italian or Roman ice cream, even though I never ate this ice cream in Italy. My two little girls picked this one even up, so it is custom right now, and I think since at least 30 years.