Funny, my spouse and I just came up with a plan to simplify some of this. We currently have:
2 checking (joint, mine)
3 taxable investment (his, mine, ours)
1 savings (his)
3 credit cards (2 his, one mine)
2 HSAa
2 401ks
The plan is move to one joint taxable account, invest the savings and get rid of that account (keep the savings buffer in checking), cancel the third credit card, and get rid of my separate checking account. So, when completely optimized, we'd still have 8 accounts!