There are 2 reasons why Pokemon Go uses look for the way to discard 2km eggs. First, if your egg storage is full, you cannot get new eggs, especially 5km or 10km eggs. Players can have up to 9 eggs, but it easily gets full by visiting PokeStops often. Hatching eggs to make space takes time.
Second, 2km eggs are worthless for advanced players because 2km eggs do not hatch into rare Pokemon. Therefore, those gamers want to get themselves available for receiving longer-distance eggs by throwing 2km eggs away.
The charts of the rarity of Pokemon hatch from eggs
Although many Pokemon Go players obviously want to discard lower-level eggs, there is no option to do that at this point. No command for removing eggs cannot be seen in the menu showing details of eggs.
How to make space for higher-level eggs
Since discarding eggs is unavailable, hatching eggs is the only way to make room in your inventory. To hatch eggs faster and more efficiently, you may want to purchase limited-use incubator. It is in the in-app shop and costs 150 PokeCoins.