Eyes are highly specialized organs for sight. Chances are that the first form of “sight” in our ancestors was a patch of cells that could vaguely detect the presence and absence of light, which was enough of an advantage for it to be selected for in that population, causing it to slowly get more and more optimized over millions and millions of years until it became an actual eye. For a structure as complex as an eye to pop into existence before any simpler sight-giving predecessor organ would be highly unlikely.