Trading can devolve into gambling, and sure there are likely more conservative trading methods that might not really be gambling, so there are not exactly bright lines in regards to the various categories, of investing versus trading versus gambling but they might sort of be on a spectrum in which many of us might not agree upon the thresholds upon which one of the practices might fall into being the next one.
Trading becomes gambling when someone who trades does not have knowledge about it and keeps on losing money. That means he is gambling with his money, but some people confidently compare these two things together, and I think they are not the same. However, the practices that can lead trading to gambling is when a trader keeps losing money and refuses to find a way to sort his problem out because when you lose too much and you are not making money out trading, that is gambling.
I think it is on the basis of risk that people compare trading to gambling and that is very correct. If you place a trade, you can lose the entire amount you exposed to risk until your stop loss is hit. Similarly when you place a bet in gambling, you also lose the entire amount if the option you chose did not work. Is there any difference in these two scenarios? You have the option of chosing what percentage of your asset you expose to risk in trading through the lot size, same can also be done in gambling through the amount to wager. So gambling and trading are similar in risk aspect.
On the contrary, holding Bitcoin is different because the only time you lose is when you sell. If you have 1BTC, this will always remain as 1BTC even if the price of Bitcoin have fallen. This is the beauty if holding because it will always bounce back and your money will be intact.