If you won $100 on the financial markets, know that someone else lost $100.
If you lose $100, know that someone else won $100.
This statement makes trading like gambling, the difference is that in trading you are playing against other traders, while in gambling you are playing against the house.
And that is not entirely true, if you trade in Bitcoin and profit, it could be from traders who want to hold Bitcoin long term, or if you buy the results from traders who are taking profits because they have been holding for a long time.
It is different from altcoins because altcoins are just speculation which makes this like gambling.