A fee? Isn't it their job to help enforce the law, being law enforcement officers?
Just like police officers at a concert aren't staffed for free, even though their only purpose is to enforce the laws and/or facilitate traffic. You could argue that enforcing those laws and facilitating that traffic is their job, but those putting on the concert are creating the need for extra law enforcement and want them on hand, so they have to pay.
I believe that here in the UK, the police will either decide you deserve an escort and provide you with one, or decide you don't need one and refuse to provide one.
I could be mistaken, but I believe bailiffs are essentially expected to take on the risk and confrontation as part of their job, a bit like ticket-inspectors on trains, or the folks that tow away illegally parked cars from privately owned car parks.
The police can and do charge for special policing of public events, though - http://www.npcc.police.uk/documents/finance/2015/NPCC%20Guid... , http://www.isanuk.org/wp-content/uploads/2014/04/ISAN-Guidan...