i think i have a rule that things should be simple...and multiple bags...cameras...watches etc. is not simple.
Not strictly true. I take your point about multiple kits potentially being complex - if their uses overlap. However, like many others, I have a number of kits of different formats that suit different subjects / locations.
Having insufficient bags for a significant amount of kit can make things very complicated and lead to forgetting things that you would have pre-packed if you had a bag dedicated for each kit.
For example, I have my Hassy 500c/m, 3 lenses, Bay 60 filters, spare backs, metering head and all the other Hasselblad paraphernalia in one Lowpro backpack. Similarly, I have my mamiya 7, 43, 65 and 150mm lenses, appropriately sized red, orange and yellow filters, lens hoods tripod mounting thingy that allows me to change film without having to demount the camera from the tripod packed into a Lowepro Slingshot 300. I have a number of other bags / systems packed and ready to go.
If I had to keep all my kit "loose" and sort through it for what I need every time I want to use it, I
GUARANTEE that, sooner or later, I would forget something really important which would set of a chain of events starting with me being pissed off and end up with my wife being pissed off with me.
I even have a spare bag (Lowepro Messenger Slingshot) for those "grab and go" moments when you just want to carry a single body / lens combo or a point and shoot.
Ergo (at least in my book) more bags = orderly life = less frustration = better end result = happy marriage.