Different methods of consensus protocols? They all achieve the same outcome - consensus - but there are pros/cons to each method. For example Proof of Work consumes an awful lot of electricity and in turn pollutes the environment, some methods are more susceptible to 51% attacks. This is almost a separate topic in itself
The fundamental idea behind a coin however is not always dependent on what consensus protocol you use. For example ethereum is planning to switch from Proof of Work to Proof of Stake but their value proposition will not change in any meaningful way.
Much like a business, a coin/token can bring real value to society. Take XRP as an example, while it has many flaws in my opinion, they are looking to improve cross border settlements. They can do what it takes SWIFT 3-5 days to do in 3-5 seconds.
I must add, I think the majority of coins are what are called 'promise coins' in that they promise to solve certain problems but never end up doing anything apart from being a wildly volatile asset. I would compare them to the many many startups that fail.
Yes I agree, people think that Bitcoin will be used as a currency for day to day purchases but this will simply never happen.
Government issued currency, FIAT, is based on trust. In my opinion since we moved away from the gold standard it has allowed for the widespread printing and abusing of currencies. This is why we see wages stagnating while the costs of houses etc have skyrocketed. There is an interesting website with some eye opening charts that you may find interesting -
https://wtfhappenedin1971.com/