Many of these things are no different than holding large amounts of normal cash(of any currency really) or something such as gold, with the exception of their being a ledger of all trades that have occurred. Also bitcoins can certainly be seized by the government should they size control over any accounts you hold coins in, take your computers, ect (it's just harder to do so).

Also I think your missing the biggest use case, abet one that isn't frequently discussed, and it is that crypto currencies are by far the best digital payment solution when it comes to the time it takes for transactions to clear. There is no dispute process, and there is no waiting on the fed for their ACA system to clear your transactions. However, I think a lot of people prefer credit cards for cash back and to have the option to charge back, but certainly cryptos are better for sellers (and potentially will give discounts to those who use them in the future).