There are multiple issues with flat bottomed wok. The point of the wok is that the liquid gathers in the centre of the wok leaving the sides with very little l

There are multiple issues with flat bottomed wok. The point of the wok is that the liquid gathers in the centre of the wok leaving the sides with very little liquid on them which helps a lot with browning. You can also throw small amounts of relatively delicate ingredients (like garlic) that will get sauted in deep pool of oil in the centre and then you can add more ingredients and build your dish. With any flat bottom you give away some properties of the wok, depending on how large the flat part is. Another nice property of wok is that because of its dome shape it will not deform even at high temperature differentials. Any flat piece of steel subjected to high temperature differentials will deform over time.