There is a monumental difference between jobs in which people get paid in full by their employer to do a job (ie fast food worker) and a job in which tips are customary because real wage is so low (ie a sit down restaurant server). As it pertains to restaurants, I always start with a 20% tip (25% or more at a fancy restaurant or or super cheap place) and adjust up or down based on service. Tour guides, PH/staff are part of the tipping culture imo. When factoring in budget, I will always pre-estimate tips. Doesn't mean I will hand out all that money. On the other hand, I could hand out more. If nothing else, these are people who are in charge of your safety and overall experience thousands of miles away from home. If tipping helps ensure your safe and enjoyable travels, it's money well spent; it's insurance. Obviously there is room for complacency, but that is where doing your research comes in to find a well oiled operation in the first place.