I merely brought 2 examples and I can surely bring more, but this is not the same as in general being able to draw a clear line on the topic. In other words, I have no clear general definition, as the topic is quite complicated and I don't think I can claim, I really understand the stock market.
Followed by
> But I couldn't draw a clear line between "necessary gambling" and "unnecessary gambling".
What? you literally just drew a very crisp line.