I agree with coler...I've used rocks, driftwood, and plants (fake) to make as many 'nooks' as possible and my mbuna have taken up residence in areas throughout the tank. Speaking of driftwood though...
the only deal is that natural woods tend to lower the PH and HARDNESS to levels that are too low for African cichlids
The extent of the changes that result adding driftwood or anything else that might play a role in water chemistry can vary based upon a number of things including, but not limited to the volume of water, the Kh of the water, the amount of wood you are adding, etc...etc...etc... Point being, it is very possible to add wood to an African cichlid tank. Additionally, I've been keeping and breeding mbuna for years in my tanks that have always hovered around the 7.0 to 7.4 pH mark and IMHO, the more important consideration is maintaining a steady and stable pH, Kh, and Gh versus trying to maintain a perfect clone of the water chemistry in a rift lake. If you think about it, it is very likely that you are buying fish that have been bred, born, and raised in an aquarium and never spent a second of their lives in their natural habitat so the more important question, IMO, is what are the parameters of the water in the LFS' tank(s). Anyways,
I really like your tank clenzpilot32 and probably agree that "need" may be too strong of a word, however, keep in mind that plants can be very useful when keeping cichlids because they allow you to break up sight lines in the tank. Or in other words, even if all of your fish have their own little cave to hide out in, placing plants in areas that restrict a dominant cichlid's ability to see a perceived rival on the other side of the tank usually results in a more active aquarium.