Very few people are swapping yen and euros trying to get rich from them.

The standard gambling that happens with "our current money system" can also happen with self-written IOUs. This kind of gambling isn't about the money, per se, whereas with crypto you get an additional kind of gambling on the currency itself.

For Yen and Euro it makes less sense since these are relatively stable, but for less stable currencies that is actually a thing. The definition of gambling you are talking about is built into our monetary system.

I give you the point that it is harder (not impossible) to enforce any regulations on these currencies. It's like cash in that sense, but it has easy access and there are plenty of options of cash, which is unlike regular cash.