Signatures have almost nothing to do with normal written script, they are a special mark that
1) is ideally hard to replicate and unique
2) may be performed by somebody who doesn't write much
Fast printing doesn't return anything useful to me (google searches are personalized so I guess we're just seeing different things). I get printshops nearby.
I think cursive it taught very formally in elementary school, possibly to the detriment of adoption, just for the same reason everything is -- grammar is given hard-and-fast rules, math is route memorization or totally algorithmic -- because it is easier to grade that way, and also because people will find their shortcuts as they age. Switching between cursive and print seems fine to me (it can also be used for emphasis).
Cursive (interspersed with print as convenient) is sort of nice because it is a fairly "normal" way of writing that still goes quickly enough. I can write cursive anywhere on the spectrum of nice and formal to quick and sloppy, in one system. Quick and sloppy basically keeps up with by brain, maybe if I was taking lots of meeting notes I'd want to switch, but it is good enough for my current applications.