The thing is Labour had 13 years in which they could have changed the voting system but enjoyed their thumping majorities so much they left it be. Any government with a majority is not going to give it up, Clegg had the chance in 2010 but for whatever reason didn't force the issue. Until we have an election gridlock there will never be a change...
Don't forget the Lib Dems *did* negotiate a refendum on moving from FPTP to (I think?) the Alternative Vote system.
I was talking to my in laws about this the other day and they had forgotten about this to the extent they absolutely refused to believe it happened, even when I pulled up the results online!
Damp squib partly as AV is such a bad system (imo).