Yes, if you don’t know a piece of trivia [such as dates], you can just look it up. So, why should we bother to learn [memorize] dates or other history facts?
Are you really going to look it up?
Suppose you are watching a TV show or reading a book. There will likely be references to history. You probably will not stop the show to go look up that information. If you are unfamiliar with the reference, it will most likely go over your head. Because you have no context, you will not likely remember it or store new information about this in your brain. However, if you do know about the historical events, you will have a deeper understanding of whatever was mentioned and probably even learn something new about it.
Knowing Dates Gives You Context
For example, you know the date of George Washington becoming president. Then, when you encounter information [through the web, TV, conversation, books, etc] about the French Revolution, you make the connection, “Oh, that was at the same time as early United States, the same year  that George Washington became president.” You can make connections about how events relate to one another.
Distinguishing lies from truth
There is a lot of inaccurate information on the web. If you know facts, you can recognize something that it not accurate.
So, if you want a challenge: memorize facts along with your kids.