Why? If the UK wishes it can allow goods in without checks. All the grief is coming from the EU. If the EU wants checks then the EU sets them up.
The EU will set up checks under no deal.
The U.K. has already said it is imposing tariffs, that means you have to have to a border to police what is coming into the and collect them.
The U.K. has notified the WTO of those proposed tarrifs and I think the WTO has already received objections.
If the U.K. doesn’t police a border then compliants will be lodged by others that the U.K. is freely allowing Irish and EU goods into the U.K. without controlling them (as we would have a competitive advantage over them) and there will be knock on effects.