Because of the recent Crypto Kitties game. Buying and selling virtual kittens on the main Ethereum blockchain. That's why the network is clogged up, people are making transaction to sell, buy, and gave birth to new kittens LOL. Hilarious. What a way to force Ethereum dev to scale up their blockchain 
https://techcrunch.com/2017/12/03/people-have-spent-over-1m-buying-virtual-cats-on-the-ethereum-blockchain/
https://cointelegraph.com/news/viral-cat-game-responsible-for-huge-portion-of-ethereum-transactions
https://twitter.com/CryptoKitties/status/937444644740198400
https://techcrunch.com/2017/12/03/people-have-spent-over-1m-buying-virtual-cats-on-the-ethereum-blockchain/
https://cointelegraph.com/news/viral-cat-game-responsible-for-huge-portion-of-ethereum-transactions
https://twitter.com/CryptoKitties/status/937444644740198400
Great, nothing says cryptos are serious investments like meme coins and virtual fucking felines.
FFS, grow up children. Time to put on big boy pants.