Your grandma could just own a token form of bitcoin.  Im not sure why bitcoin should be more complicated then a national currency, it could be handled or presented easily enough by various entities.   All that really lacks is confidence and regulation, so you end up relying on each company providing a service of convenience for bitcoin not to be neglient in their security or other risks.  Like we saw with exchanges thats where it can go wrong.    Thing is with national currency originally, banks did fail and it was just isolated to those customers judgement and the brand they invested in.  They now have central banking and largely its a system controlled by one point of failure with government and unfortunately it is failing.    
I think I prefer the small split up risk of dealing with each company and the bitcoin unit itself retains integrity.  now we have the opposite where every unit of currency is being devalued

bitcoins should be made as simple as possible, shed the elitist cryptographic Im a fricking genius to totally understand this protocol default stance and make it as modular as lego.  Having a clue how it works should be incidental and in no way indicative of success of use,  if that attitude never changes then yea its not going to be more then a tech sideline.
   Some other populist remake will actually take off, its usually not the inventor who succeeds but those who develop and assimilate it into the common consciousness with least trouble.   Nokia came up with a smart phone concept before Apple for example, they just had no where as much savvy in bringing it to customers, I think they just kept it back for fear of overcomplicating simple devices.
IBM invented the PC but never captured the market, its a regular theme for this to occur so it might with bitcoin possibly

   Whoever develops this whole mass market approach needs only do one thing, which is to ask themselves can I use bitcoin while drunk because if thats still possible then its probably become easy enough for mass adoption