Put that under your digital mattress
Bitcoin (BC) has a niche, a bit like Penny Blacks (PB) or Pokemon Cards (PC). Liked by nerd/collector types of various kinds, essentially human media artefacts created in limited quantities. BC has a couple of other interesting properties in connection with decentralised protocols for creation and transfer of these limited edition numbers. Maybe like PBs they will be valuable to a few nerds for a long time or maybe like PCs they will have occasional comebacks but will die the way of all such crazes. Maintaining a collection of PBs or PCs doesn't place a liability on the electric supply, and as far as I can tell most of the electricity used to maintain the BC system isn't paid for by the operating beneficiaries, it's provided by spotty faced teenager pool members' parents, by BOFH employers and by physical owners of botnetted PCs.
PCs were also a playground currency for a while, but no idiot ever claimed they would replace double entry book-kept money. Banks may charge exorbitant fees for book-keeping, but they can afford to reimburse you when something goes wrong and regulators require they do. Cash is non-repudiable and once it's gone it's gone, so only suited for small transactions unless you're into criminal activity. The security infrastructure we pay for in bankers' bonuses, drug dealers pay for in costs of protection, violent means of payment enforcement and drug warfare. BCs cost more in electricity than they are worth but that's an economic and environmental externality like the cost of the Victorian polluting mill-owners effluent stream, see who pays the bill above.
As to keeping your BC securely, maybe you can manage that risk if you're smart enough, but even botnet operators risk getting caught and doing jail time. And they can inherently do the BC risk management most securely of all, being able to operate through a different chain of proxies for each transaction to avoid giving away real location IP addresses. Even if you've managed to remember your BC numbers or keys and don't have copies other than in memory, you'll still be vulnerable to rubber-hose cryptanalysis at the last resort. See also the RIPA in relation to the willingness of the state to use imprisonment to obtain the crypto keys it wants.
The moment someone successfully uses BCs to purchase a hit, then all the BC to cash exchanges will be shut down as potential accessories to the crime and the BC bubble will then burst. Seems DPR the Silk Rd founder tried to use BC to buy a hit, but didn't succeed.