Technology.
Everything got better, likely with unintended consequences.
There are a number of torn up rail lines in Alberta. Trains used to have to stop at intervals for water. There were a number of rail stops and sidings for trains and rail crews. Trains improved over time and the need for multiple rail stops decreased over time. A number of rail stops had accommodations for crew, sometimes a general store, sometimes a small town of some size. A lot of these places disappeared entirely over time. Some of them are not even names on a map anymore. The need for multiple rail lines themselves became redundant. Tearing them up had a devastating economic effect on many places from which they would never recover.
Farming became more efficient. Years ago there were gangs of workers that travelled from farm to farm during harvest. Mechanisation made them obsolete. There used to be small towns all over where farmers used to travel to for what they needed. Things had to be within a certain distance and accessible. A lot of times you would see farm equipment dealers in small towns. Not so much anymore. General stores which were in every town now do not exist. My father grew up on a farm. He mentioned sitting on a steel tractor seat enduring the summer heat and dust. Now you have sealed air-conditioned cabs with satellite radio and GPS. You can do a lot more with less.
Roads improved, vehicles improved, people could travel longer distances. Everything got better and more reliable. Small towns used to have gas stations and mechanics. Even the cheapest car you can buy new these days is pretty reliable. My grandfather had a garage and shop in Tomahawk, Alberta many years ago. He would not be able to do it in this day and age, there are less people and no market. I remember it was fairly common to get a flat tire. The tire technology has improved so much that getting one is almost rare.
With better roads, better vehicles, transportation got cheaper and more efficient in the process. This had a ripple effect, you could travel further and were not constrained by being where you lived. You have more choice. Unfortunately smaller places often could not keep up, compete, or there was no longer a reason for them to exist.
Technology is a large part of it. Two world wars stripped a lot of towns of people. You read cenotaphs in dwindling or abandoned places and it is amazing how many people from small places served. The wars also diverted funds for irrigation projects and roads that doomed some places. Consecutive years of lean harvests sealed the fate of others.
You read in the news that some small Alberta towns are offering incentives such as free land with a stipulation that you have to build a house on it to get people to move and live there. The sad reality is that I believe it is a losing battle and they will be unable to reverse the decline. That way of life is no longer there. I think we will eventually see a small number of large populated areas with less and less in between. I do not necessarily believe things were better years ago, just different. The landscape is changing.