we have wood effect karndean through the bottom of our house - hall, loo, kitchen, little sitting room. 2 kids and a dog so it gets hoovered every day at least once, and mopped/wiped at least once every 2 days. if run a bit of wet kitchen roll over it in between times, mopping up a spill or whatever, it comes away black! and I was mortified to notice how dirty dds friends feet were after running around barefoot 
we take our shoes off but I never ask guests to, but tbh we have very few guests! so why is it not cleaner?! honestly I feel like I spend my life cleaning the floor, am I doing it wrong? !