Tipping an independent provider of services is not required or reasonably expected.  However, when you get into the non-independent world of service providers, then the issue of tipping may be appropriate, depending on the service.  However, everything comes with strings attached...including tips.  Some people use it to try to gain leverage in the relationship, and sometimes it is an attempt to make you pay less attention to your safety.    I "had a dream" about an undercover operation where the hard working operatives tipped very well each time they had to drag themselves in to work and obtain services for months as they diligently made their case against those receiving "generous" tips.  Let the tippee beware.