I puzzle over surname extinction

Goodbye, Mr. Chips (1939) movie title

Goodbye, Mr. Chips is the name of a 1934 novel by James Hilton and a 1939 film, which I once saw, about an aged school teacher and former headmaster of a boarding school. 

One thing that puzzled me was the eponymous character’s name.  I've never actually come across anyone with the surname Chips. I imagined it was a made-up name and I wondered why.  But last week I found out that Chips used in fact to be a fairly common surname which has died out.  It's one of tens of thousands to have disappeared in the UK over the past 100 years, research has shown. Others are Hatman, Rummage, Nithercott, Raynott, Temples, Southwark and Woodbead.  Clegg, whilst current now, faces extinction; and is likely to be joined by William, Cohen, Sutcliffe, Kershaw, Butterworth and Greenwood.

The research has been carried out by the Ancestry family history website. They compared surnames from the 1901 census with names from modern records and found that many had disappeared, and others are becoming rare.  William for example was the 374th most common surname in 1901, but has fallen to 12,500th.

Various media have carried this story, often spiced up with witticisms at the expense of deputy prime minster Nick Clegg, or references to the title of the Mr Chips film, in the Guardian for example.

But there's a puzzle here. What drives these trends? A few explanations are offered but strike me as inadequate. Many vanished surnames were later anglicised by their owners, including immigrants who changed their name to avoid complications with foreign spellings. Yes I can understand that one; but of the examples given, this seems applicable, if at all, only to Cohen.  One dreadful explanation offered is that the first world war played a part in wiping out some names when specific battalions suffered mass casualties, with towns or villages losing a whole generation of young men.

But what other factors are at work? What’s driving the extinction of Clegg and Sutcliffe today?  Sutcliffe might be a special case I suppose, being the name of a notorious Yorkshire murderer convicted in 1981. But did large numbers change their surname as a consequence? I doubt it. Things are going on that I don't get. I hunger for further explanation.  Whom to ask?  A genealogist? A mathematician? A geneticist?