While some tourist guides perform tours as a sideline business there are other guides that perform tours as their main business and who are passionate about their work.
Most of the tourist guides who work for bigger companies are not allowed to have their own touring businesses, so although they have good knowledge and experience, they sometimes lack the passion a guide would have that operates on his / her own. The tourist guides who work for themselves often will take more initiative and create unique opportunities and would more likely go the extra mile to make your experience with them an unforgettable one. These guides obviously work much harder because they have to pay for their own marketing, build up their own contacts on route and do all the planning, administration, bookings and transfers that are associated with tours.
Again, this is so frustrating when a tourist guide working for him- or herself would get an opportunity to transfer a potential client from the airport after their arrival in the city, informing them everything about their services, to then lose any potential tours because they simply cannot compete with the bigger companies who can afford to make their tour prices cheaper. So when the client arrives at the hotel and get bombarded with all the brochures from the bigger companies, most people tend to then favor the cheaper options (even if they get much less value for their money). What makes it worse is that the people at the hotel all get commission from these companies (in most cases 30%) when bookings are made to them so obviously these companies would then be recommended rather than a tour operator who works on his or her own.
The tourist guide who works on their own loves to work out an itinerary for the days you have available in the city according to your specific wants and interests. For example a specific familiar route can be planned with part of another route in one day to accommodate your specific interest, whereas the bigger company might cover these areas in two different routes on offer on their brochure. By discussing and planning all ideas with a tourist guide, he or she could give you an itinerary in the end that may just as well cost the same or slightly more as when you would take the cheaper options adding up as 3 or 4 different scheduled tours. In other words you will still see and visit the same attractions you would have with the bigger companies (who seems to be cheaper then) but in 2 days rather than 3 or 4 half day tours etc. This creates more time and days to explore the area.
So if you are a tourist, or simply on vacation anywhere, take some of the aforementioned into consideration before taking the selection of options the person at the concierge desk will give you. Do a bit of research and you will find these tourists guides who operate on their own. It might cost you a little bit more, but with so many more events and places to explore that in comparison, you get a lot more value for the money.