Tis an individual thing really.
We remove ours for summer use and refit for winter use, and we always remove shoes when stepping into the van!
The van will stay warmer with carpets and without as someone said earlier, if you have a double floor with floor trap doors, no matter how clean you feet are, dirt will go down the trap doors and sit onto of the water tanks.
The first thing I did when I got my Duetto was to remove the carpets and store them. But now I am getting the Hymer I am wondering if I should leave them in.
Do you have carpets?
I installed same with previous Dethleffs. Would consider same for current N&B and, concur with your above comments. Our local Costco supply tile, cheap as chips. See clip below, not exactly same, but similar.
[video=youtube;QVmUmn5TN_E]https://www.youtube.com/watch?v=QVmUmn5TN_E[/video]