Sub-woofers are an interesting phenomena in that they are relatively rare in 2 channel systems in Europe, where they are found mainly in AV theatre systems. They are, rightly or wrongly, often perceived as unnecessary to a pure 2 ch system. The theory being that if a speaker is done right then you shouldn’t need one.
The US market seems more fixated on them, and in the plural as they seem to come in multiple subs in some US systems.
We have smaller rooms in Europe, maybe that’s why too, no room for more wooden cabinets. And we rarely have room for a dedicated Hi-Fi room, usually it’s a home lounge too. If your room only takes a small speaker, that is the type of speaker which most benefits from a sub, then you’re unlikely to be able fit more boxes in. If your room fits a bigger speaker you shouldn’t need a sub.
When I have heard systems with arrays of multiple subs they have sounded to my ears too much. Or when toned down I have heard them sounding good, but not 4 boxes worth of goodness.