- They provide no meaningful consumer protections (since this necessarily requires an authority, which blockchains may not have)
- They don't protect at all against meatspace vulnerabilities like scams and other deception-based attacks, which are by far the more common issue in banking. This is exacerbated by the lack of consumer protections.
(To be clear: don't read my comment as being in support of PayPal. They have abused user trust for a while, and I haven't had an account there in over a year -- fuck 'em.)
There's a reason most people in well-banked countries use plastic over cash these days, convenience and consumer protection are it; and even with cash, the barrier to entry for fraud is higher since at some point that cash will come into contact with the banking world, and will have to be accounted for. If your cash flow is suspicious enough, it'll be audited.
Or less snarky: it's simply harder to steal something or defraud someone in meatspace than in the Internet, so less protection should be necessary.