I live in Europe and for the last 15 years taxis prefer to be hailed via phone/sms rather than hailed on the street. If you hail a cab on the street you will get a higher rate plus a hailing fee. Cabs near airport/railway station that are parked there are a tourist trap since they charge almost triple price plus drive you a longer route. Basically a taxi company strikes a deal with city council so only their cabs are allowed to park there and then make their "hail from the street" rate as high as local laws will allow.