That's indeed a very interesting question as the answer is complex since it's very ingrained into the specific culture you might be referring to.
Tipping is seen and understood very differently in different cultures -and note I say "culture", not "country" because it so happens in some parts of the world (ie here in Europe this is very common), political borders do not necessarily match cultural borders or, as it often happens, several cultures with different traits and ways of doing things might be co-existing within the same country. Furthermore, tipping is also a very delicate matter since "more is not always better", on the contrary, sometimes over-tipping is perceived as rude and offensive and in some cultures tipping in itself is not part of the traits of that society.
To complicate things more, it's sometimes also a generational thing. For example in my own culture here in Catalonia -which is very "egalitarian", and "fairness" is always important- elderly people tend to tip more often but younger generations not necessarily. The reason lays in the fact we had something called "minimum salary" incorporated in our legislation in the 1960s so nowadays everybody gets paid, at the very least, a "minimum salary", that is annually agreed between the Government and the major unions, and which is automatically increased according to different parameters, normally indexed to inflation and cost of living, albeit lately is rather more a fixed %. So, "theoretically" this allows a person to live on one's earnings. Yet this is debatable, of course, because the cost of living is not uniform across the country.
This "legal safeguard" changed over time the tipping culture of younger generations since now the helping the worker to reach ends meet was no longer needed (again, theoretically!), nowadays, tipping is more related to service, or rather the perception of it, the fairness of the barter: has the person serving/attending me gone beyond what it was expected?, if so, a tip is given, if not, then no tipping.
So, for example, "tipping" here in my homeland, and in my city: Barcelona (and in my generation, 35-54) generally speaking works by "rounding up" the bill, and only in the services industry, of course! Let's say you take a taxi, and the fare is 10.80€, you'll round up to 11; you have a snack in a coffee shop and the bill is 23.60€, you'll probably round up to 25; the same case on a restaurant with a bill that's 114€, that might be rounded up to 120€. As you can see in the pattern, tipping is somehow related to the total amount... but only (only!) IF the service received is perceived to be beyond expected.
No tipping is perfectly acceptable and is also common -regrettably, a lot of people in the service industry don't see the need to go beyond what's expected.
I believe this "introduction" was necessary and important since this is a forum with a large chunk of US members and the tipping culture in, say, the restaurant scene there is rather different ---and, if I may, despairingly abusive from our point of view, although I understand your labour circumstances are different.