A good way to show appreciation for the work a locksmith has done is with a 15 to 20% cash tip at the time of service. There's no need to tip a locksmith, as they don't expect tips. Although it's a service job and a local locksmith doesn't like going out late at night or very early in the morning, it's their job and they get paid a decent wage (or they own the business). There is no need to tip a locksmith.
It can be a nice gesture in certain situations. This includes bad weather, vacations, and difficult tasks. If you decide to tip, stick with 15 to 20%. Locksmiths don't expect tips when setting their prices.
If they needed to do more, they would raise their prices. Most people don't tip locksmiths. The reason you think that is because you see it from a worker's point of view. The point of view adopted is that of someone who broke his back to build something meaningful.
I also declared him a worker. You also have to look at it from the point of view of TRADE. How are you going to work in a legitimate business if you accept tips? It damages 100% OUR LEGITIMACY, but when it comes to your own pocket, it's clear that you prioritize that. In addition, if you accept tips, it impairs your ability to bill the full amount.
The reason they tip is because they're thankful that the value of what you did outweighed the value of what you're charging. Basically, you're leaving the customer behind and instead subsidizing the full amount of what your work and skills are worth in exchange for the customer's kindness. This is not conducive to any long-term relationship.