> Leaking lift gas is expensive & difficult to prevent. Also explodey! (if H2).
Expensive OR very cheap and explodey. (Gasoline is also explodey)
Helium is comparatively expensive, but you don't expend it as part of normal flight and it doesn't migrate very quickly through modern materials. A bigger problem than loss is fouling - you have to pump out the helium and purify it every so often (I think Zeppelin does it every six months).
Leaking lift gas is expensive & difficult to prevent. Also explodey! (if H2).
Airships have to have enormous volumes to float. Therefore they have a lot of drag compared to their payload capacity (Vs. heavier-than-air-craft). So they aren't very good at dealing with wind in an efficient manner.