you got something wrong! not "everyone" thinks that. and that is why bitcoin is strong. and it is not just something you invest in and make profit. it is a unique decentralized payment system that can not be controlled, censored, restricted, or anything like that. and all of these attributes are making it strong. these are the reasons why more people are going to buy (aka dump their centralized fiat for decentralized bitcoin) bitcoin and why its price will go up. not because there is more profit on their centralized fiat.
Correct, one of the great problems with fiat is that it needs the force of the governments behind it so people accept it, people do not see this because it is happening every day and there are many countries in which only the fiat printed by the governments is allowed to circulate, so if you want to use dollars you first need to convert them to the local currency.
Bitcoin is different, right now most people disagree with the utility of bitcoin, this is easy to see since they have not adopted bitcoin and yet bitcoin is still very strong despite the different bans and regulations put in place, if it really becomes widely adopted bitcoin will become easily the strongest and most resilient currency in the world.