I also believe Jersey is not as popular as it once was. Although the price of flights can be cheap, and there is no VAT on the island, it is not a cheap place to stay.
Having been several times in recent years (because I like the place) it is probably cheaper to go some where like Spain.
Jersey has occasionally been daily over the years, certainly in 1998 Jersey European (as it was then) did Jersey daily via Guernsey with a Friendship. I think British Midland went daily in the early 70s.