Don't understand why flexbox is needed

I don’t understand why to get the navigation bar (i.e. mission featured tea etc.) you need flex-grow 1, or else the image and the title get stuck together.

@mtf @codeneutrino Hey guys sorry to bother you guys, was wondering if you knew why nav requires flex-grow for it to go to the right, or else the logo and the text in nav go side by side.