I think people who doubt the purpose and function of using bitcoin are those who often panic when prices fall. because they don't have any grip and belief in bitcoin. whereas the main advantages of bitcoin are clear, that anonomity and decentralization are the main attractions of bitcoin, and you can say that fluctuations make bitcoin unsuitable for currency, but the fact is that many merchants and users use bitcoin for it. Bitcoin is needed for many reasons, and including what I mentioned.
First and foremost, people should first learn and understand the difference of market terms such as pice and value. Price is changing, value is dominance. Why dominance? since whenever a crypto's market price decline, its value will remain the same as it suggest the potential of the coin to get back better in a latter time. Some newbies and impatient's doesn't know that, as a result, they tend to panic sell and worry about their investment.
Yeah, they can't interpret that so when prices fall, then their alarm will ring and panic time starts. they are too focused on bitcoin prices that down quickly, without considering the "value" of bitcoin which is still very worth, even though that the reason why bitcoin will back raise.