yes nowadays bitcoin holding is a good source of investment if someone will wait for a longer time with their money and will not spend them or sell them then they will earn a good income when the price of bitcoin will rise in the future.
Holding is a great way to make profits in future but the only issue with holding is that it will never increase the number of bitcoins in your wallet and it will remain same in the future and you will be making profits with holding only if you have enough amount of bitcoins and that also only if price goes higher in future and holding will never multiply your coins.
You are right that holding coins won't multiply the number of them, but if you hold bitcoin, you probably do it as a form of long term investment and if you compare it for example with gold, bitcoin is definitely better. Not only because it is a virtual item, so you don't need to physically store (and secure) it, but also the liquidity of btc is much more better. The biggest advantage of bitcoin is that your investment can be transformed into payment instantly.