Barcelona is blighted by street crime
Pick pocketing, bag-snatching and robbery are endemic in central Barcelona, mainly due to a small number of criminals who are known to the local police, but the police do nothing unless someone ends up stabbed in hospital. You can be robbed within yards of a police officer, and their only response will be to tell you to go and make a statement at the police station (which will take 2-3 hours due to the apathy of the police and the number of people queuing ahead of you to report that they have been robbed too, if you passport was stolen you can add another half day at the UK consulate getting a temporay replacement to re-enter the UK on). This streetcrime amounts to millions of euros per year in thefts from tourists, maybe with some VIP victims and bad publicity the city will start doing something about it.