For me, it was a combination of budget, room size, and general aesthetic preference. I didn’t find any real advantage to spending more for towers. My cinema room is also very small, so the added “benefit” of additional drivers is not contributing much in such a small space. Lastly, I just honestly have never loved the general look of floor-standing speakers. I much prefer the placement flexibility of a monitor in most cases (especially when they have VESA mounts like Arendal <3).
In my experience, a lack of a “fuller sound” is almost always helped by the implementation of multiple subs (at least two). If it’s a smaller room, even two small, well-built subs can do more to balance out a room than what most people realize.