What it is & Why it's there
This is the 'sole plate' and is only visible in scenes/views to do with structure. The sole plates are included in your model because they are typically required to frame a door (and needs to be quantified).
Do we show it to our clients?
Unlikely. Customers/clients don't normally need to see anything to do with the structure of their home. The presentation scenes (or Structure-off scene) are used to show your design to a customer, and do not show the sole plate.
If you don't require a sole plate to frame a door in your model, you can leave it in as wastage. Alternatively, when you have finished modeling, go around and manually delete each sole plate so that they are not visible in the structure scenes, and aren't quantified.