I like Simutrans [0], in which people want to get from A to B and are willing to change between bus/train/plane. The routes which are central to one's network really need to be able to bear a lot of passengers.
There were attempts to introduce more simutrans-esque behaviour in patches called cargodest, but it proved to be unacceptable performance wise for the map and network sizes that OpenTTD uses.
And without cargodest, what is the point of OpenTTD? I honestly struggle to understand this game if passengers appear randomly and pay the full price to go wherever you like to take them.
It's probably also worth mentioning that cargo quantities are usually more limited at first. Primary cargo especially grows slowly. Passengers can grow very quickly if the player understands the city growth mechanics (the count is a function of city size), but even with cargodist if you make an actual network they will dictate their stop.
For me the appeal is more the mid-late game micro-optimisations, like how to make a junction work when there's constant incoming trains.