The two diesels cut up in 1980. Let’s all remember that the diesel preservation movement was not has strong then has it is now. People did not have the ‘spare cash’ that seems to be available now. Remember, mainline steam had largely disappeared less than twenty years previously. Depending where you were living, just twelve.
If they had serviced another five or six years, they may have been preserved has static exhibits.
Also, an entire generation or two, have grown up only knowing diesel and electric traction. For those who grew up with steam, diesels and electrics, where the work of the Devil.
Many years ago, about the time these were cut up, there was an article in Steam Railway called Damn Those Diesels. If I remember, it was about people’s reactions to persevere diesels on then called preserved railways.