It's not nececery. The beauty of that is that you can build whatever you want and put that together whatever you want. For example I have a space 5x3 meters. I will fix there 2 end stations + nice peace of curved and straight tracks. if you have enough space you can make it as a round layout, if you are limited in space, you can do end to end one.
The most important is that you do not need a massive space to build it. You can see on my photos, that I'm usually work on single module at the time.
They are easy to store and you can put them together when you want. Imagine the track from the