Lufthansa
Lufthansa are a masive airline group and at the end of the day they fly to & from where ever there is money to be made, the number of pax flown is only a part of the story- as i'm afraid these days its all about yield.... making money.
LH have tried several flights from regional airports in the last few years and if they don't make money they stop.
BHX my local airport they tried Hamburg (at very poor flight times) that lasted less than 1 season, also tried Cologne (with LH & German wings)
I do think Berlin to BHX would of been a route to try that would make money.........
so i'm afarid at the end of the day all airports are going to have flights that start & stop... if its not making an airline money why operate ?