I have never been a fan of handbags because I simply cannot see the point of having several items that perform the same function. Mind you, shoes are a different story entirely!
The main reason that multiple handbags are not appealing is the fact that things need to be constantly moved from one to the other and the chances of not having the item you need are substantially increased.
You may remember that I recently bought a bag for work that would hold the laptop as well as anything else I need to take to work. Here it is with the everyday contents.
This has worked well and I have not even used my regular handbag since buying this one. If I am going grocery shopping I just grab my phone and purse and toss them into the tote bag I use for groceries.
This all changed last week when I went to a funeral and neither my work bag nor a shopping tote were appropriate. I retrieved my black handbag from the shelf in the wardrobe. The only items in it were a mini tape measure and a pen.
I added my purse, phone (and charger) and keys and I was ready to go.
I realised that everything else was really only applicable to work so it made swapping bags relatively simple.
organised castle 
I too have only one main handbag, but don’t always want to carry it, for various reasons. So I’ve developed the habit of putting the stuff I always want to carry where-ever into a smaller bag inside, so that’s the only thing I have to grab when I need to swap bags. In theory. 🙂
I like your theory. 🙂 My ideal would be to not have to carry a bag at all. I need a lady-in-waiting but I don’t think that is going to happen!!
I bought a handbag a few weeks ago whilst travelling, and just did a wholesale transition of all contents. The up side is the new bag is bigger (but to date, not more stuff in it) and lined in a light fabric making things easier to find, save for it being more rigid and a more solid structure means it doesn’t flop open to find things as easily. I don’t intend to move handbags regularly – only really ‘going out’ in a nice outfit/occassion might I scale down. I have perhaps four handbags that are suitable for work (all fit A4, two have short straps for my elbow, and two for my shoulder). I probably could have less, but I like and use them all, so they stay!
A light coloured lining is a great help when looking for things in the bag!