Toilet situations are definitely personal to each person. To some, it’s no big deal and to others, it’s pretty important. For myself, it’s important, especially since I’m looking at living van life full-time and long term. (Permanently, unless something happens to cause me to be unable to.)
Also, being someone who lives more minimally than most even conceive, I’m happy to give a five gallon bucket the space. Space may be minimal in a van but if something can perform double-duty (seating and storage, for example), it’s worth the space. A five gallon bucket is always an extra, moveable seat.
Storage is not a concern for me. A few dishes, toiletries, food, clothes and books. I live so minimally that, if I needed to, I could pack a backpack with a couple changes of clothes, some toiletries, my Bible and walk out the door and never look back. But, that’s just me.