Just that really. I've had my car around 4 years and can count the amount of times I've cleaned it on two hands. Lugging buckets of water downstairs, having to go back up three flights of stairs again to refill / clean the sponge is just a pain in the arse to clean it on the outside, and that's not to mention the inside which is frankly disgusting despite my halfhearted best efforts with a handheld dust buster and wipes. Mud and debris all over the floor. Dirt from DC shoes on the back of the seats. And then there's all the crap from nearby trees which seems to be permanently embedded in every crevice... and I'm fairly sure there's moss growing in the door seals which a toothbrush just isn't shifting.
If you live in a flat and have a car, how - and how often - do you clean it?!