Hence the comment ‘futile gesture’.
The debt remained, any processes to repossess rolled on & the risk of homelessness remained.
At the time, people did post - or rather put - the house keys through the bank/building society letter box as a desperate measure or as expression of desperation. It was a very difficult time, particularly for those who had recently bought high as many tipped rapidly into negative equity. Most were in a position where they could stay put, keep up the repayments & ride out the storm. But for some who needed to sell due to partnership breakdown or couldn’t afford the repayments, being forced to sell inflicted a sever financial blow.
The brutal reality is that in the late 80s, some people lost their homes through repossessions, & any remaining debt after the forced sale was still owed to the lendor. It took many years to pay off that debt with nothing to show for it.
As @Blossomtoes points out, repossessed houses were sold - often at auction - so that lenders could quickly recoup their money as a lump sum or a new consumer loan.
As @Mark19735 points out, lenders will go some way to help problems with payments by reconfiguring the debt. This is far easier done face to face with someone in the branch.
My point is that consumer borrowing now, compared to the 80s, is now mostly online & the opportunity to speak with someone - dare I say friendly - in the early phase of struggling with payments is less likely.