because the facts speak for themselves. Many, MANY out there are not tribal with their vote. Not Liberal no matter what. People vote with their wallets and what they believe is the best. The UK is on the road to a pretty good recovery after an almighty crash in 2008. The facts back that up for enough people in their lives. Zero Hour contracts to many are a good thing (66% of those on them WANT them to remain) and the NHS being saved is offered by Labour every single election. When it does not need saving.
The Liberals this time just didnt really offer anything. Other than being in the middle. Hardly something to grab for those unlike you who will vote for who ever is best for them at the time, regardless of what party that is