It's true, but it's not so simple.
Imagine that you live in Italy, where only 24% of the population lives in cities with a population equal or larger than 250 thousand people.
Half of Italy is not flat and it's very hard using the bicycles to move, unless you are already expert and even for bikers (as in motorbikes) it's challenging going up and down the hills and mountains and usually they go in group.
Paradoxically around Milan (and in the city) they use bikes a lot, but it's also one of the most polluted areas in Italy because they also use cars a lot to move from or to Milan and other large cities, mainly to go to work or it's trucks moving goods.
You can't replace them with bikes.
You can't replace them with trains either, because regional trains are already at full capacity and Milan public transport already moves 800 million people/year (fun fact: the Milan public transport company ATM also operates the Copenhagen's subway).
Being on flat lands surrounded by high mountains also means that there are no regular winds cleaning up the air, so paradoxically biking is more dangerous for your health.
23% of the Italian population (13 million people) lives in cities with a population between 20 thousand and 59,999 people, the majority of towns in Italy (20% - 1,509 of them) have a population between 1,000 and 1,999 people and host 2.5 million people.
Those are the areas where they can't give up on cars, they have no alternatives, they have to use it daily for every activity: from groceries to work, school, church, etc.
They are usually near highways or heavy traffic roads, because many people move daily to go to larger cities for work, but also the areas where biking it's more of a challenge.
So it's a combination of long distances (people live away from cities because housing it's much cheaper), geography and older population.
I present you a sample of the area where my parents come from.
https://www.juzaphoto.com/galleria.php?t=2681540&l=it
https://www.juzaphoto.com/galleria.php?t=2510258&l=it
https://www.juzaphoto.com/galleria.php?t=2510257&l=it
https://www.juzaphoto.com/galleria.php?t=2253636&l=it
https://www.juzaphoto.com/galleria.php?t=2129996&l=it