I think for the British....it’s not much of a deal. For the EU folks, they demand this. Another of the dozen reasons why the negotiation talks were run by comedians with no intentions of building a true agreement.
A month after the exit (now virtually guaranteed I think), the US will step in and there’s going to be one of the biggest trade agreements of the past fifty years signed, and the UK will be a major partner. I will admit, there is a recession coming and will hurt the US and the UK...but it’ll harm the EU just as much.
And on that you're wrong - both the UK and Ireland/the EU don't want a hard border.
The EU folks are demanding that the UK live up to its promise on the good friday agreement for no border.