Why do you think that no one is willing to buy bitcoin? Bitcoin is not popular nowadays
Hell no!, bitcoins popularity literally has spread all over the globe,with adoptions in more and more countries and continents,even the government is adopting it's underlying technology(the blockchain technology),as it has been used to conduct elections in some countries..
The demand for bitcoin only drops when prices drop,as users try to cut down on what they feel could potentially be a loss..
This fear and uncertainty been created right now as a result of a downturn price is one reason why the demand has dropped,but looking at the btc charts,we can be hopeful of a recovery definitely
It depends on the situation and who will be the holder of his bitcoin account. I will recommend to the family of the mentally retarded person the bitcoin but not the mentally retarded his/herself. He/she cannot understand the situation and /or the system and even on how she/he will do to the bitcoin. I will tell to the family the benefits and the insurance they will get once they start joining bitcoin that they could help them to provide the needs of their retarded family member.