We use very little plastic, but I'm also admittedly incredibly picky over stuff being dry. It could be water dripping from the plastic racks above; nothing is truly wet, just enough that I'm not willing to put the dishes away without further drying.
I think plastic has a lower thermal conductivity/mass. Heat moves into the plastic more slowly and it just doesn't hold as much energy thus doesn't get hot enough to make the water evaporate.
I think plastic has a lower thermal conductivity/mass. Heat moves into the plastic more slowly and it just doesn't hold as much energy thus doesn't get hot enough to make the water evaporate.