Nope! The humidity dome is used to promote strong root growth early on in the growth cycle. This is important because by increasing the local humidity around the plants, you actually decrease transpiration and subsequently photosynthetic activity, which forces your plants to grow a strong root system. With a strong root system you'll get shorter and more stable growth.
Having said that, the humidity dome is not required to have successful growth. Depending on where you live, the natural environment may provide more than enough humidity for your plants.