Most people use Babel for transforming ES6 into ES5. Before Babel 6, Babel did that out of the box with no configuration required. With Babel 6, it basically

Most people use Babel for transforming ES6 into ES5. Before Babel 6, Babel did that out of the box with no configuration required. With Babel 6, it basically stopped doing anything out of the box, including the main thing it was famous for doing. While it is admittedly not a vast amount of effort to make it do precisely what it did before, I'm sure you can at least sympathise with people who found it strange that you have to include a "preset" to make it do the main thing that you expected it to do.