A lot of Youtube videos is showing subway tiles being installed without spacers... Do you really need spacers or not for Subway tiles (Bathtub surround tiling) ??
4-1/4" and some larger wall tiles have bumps cast in that act as spacers. Unless you want a larger gap, no additional spacers are needed.
Whether your particular tile has them is uncertain. They're often necessary to prevent sagging with heavier tile while the mortar or mastic sets.