They are used to enrich the flavor of the bread and also to give a moist cake - like texture and a very soft crust. (atreatsaffair.com)
And on top of this they provide a great crunch factor to a rather soft crust! (familylifegoals.com)
If you like your breads to have soft crust tops, you can brush the top of the bread dough with egg wash (containing 1 egg yolk with 1 tbsp milk). (bakeforhappykids.com)