Why would it be vanity flying?
Even though a quick look at prices for next week suggests it hasn't massively attracted people the way they might have hoped, it was a good idea that showed a level of local knowledge that airlines all too often lack and that is nevertheless set to be a
PR success.
That said, it's clearly not a viable long term route against a normal train service operating at really quite a high frequency (even though the trains are often deeply unpleasant) and that is soon to have better connections with the part of London that LCY best serves..