Excluding gameplay reasons, wouldn't be cool to be able to find Pokémon eggs in routes or hidden in cities? I remember an old mechanic about using cut in tall grass to getting rid of it, something like that could work but destroying the grass would uncovered a hole where some Pokémon lay eggs that may or may not contain one, just an idea.
Sure, the daycare would still exist for your Pokémon to breed.
Pic unrelated