I don't know why people say bitcoin is gambling. Its not gambling. You are investing your money and time. You use your internet. So its not gambling dealing with it.
It's only gambling if they don't know what they are doing. They will invest in bitcoin without even studying its principle, use, and other things. All they want is to gain money quickly that's why they call it a gamble. They are also the people who panic sell and say that bitcoin is a bubble after that. Let them be.