Why is the flight deck tilted upward at the bow? It has no airplanes.
But it could.
They are in the customer list for the f-35.
Officially, because the Spanish design, they are based on had the skijump (the Spanish fly Harriers off theirs) and it was cheaper to keep it rather than redesign.
Unofficially - while there are no official plans for the LHDs to operate as small aircraft carriers, keeping the skijump gives us more options for the future than getting rid of it. And even if we never fly our own planes off it, an extra deck for British or US Marine F35Bs might be useful in some joint operation in the future.