Because of the recent Crypto Kitties game. Buying and selling virtual kittens on the main Ethereum blockchain. Literally just a virtual character on a website. Like collecting pokemon in Pokemon Go except that it runs on the ETH blockchain and the only way to add new kitten are to buy or gave birth to it. Both done on ETH chain and people somehow love it. That's why the network is clogged up, people are making transactions to sell, buy, and gave birth to new kittens LOL. Hilarious. What a way to force Ethereum dev to scale up their blockchain

https://www.cryptokitties.co/
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