It isn't like a stock. Equities going up is good and will have periodic retreats. It is a company and supposed to gain in value.
A currency is a medium of exchange and unit of account. It is supposed to remain stable. It shouldn't go up or down like equities. It should be stable. The unit of account changing would be like a unit of length changing. Try building a house if your measuring device was constantly changing in you.
All currencies live and die on market pressures which require societal trust. An exchange of one currency for another is an exchange in preference of trust. Stock is the exact same thing, with the value a measure of trust in the given corporation and the viability of it to survive in a given economic, industrial, or political environment. To equate that they are different is to speciate an argument for why one set of matter and social construct is eternal in nature and the rest are mortal in nature: it is a highly opinionated point which one must make which in itself proves that the argument is false.