Well traders can be also called as investors to, the difference is the intention and the length since most of the traders accumulate some crypto for short term purposes only. That's the reason why other people also call them as a gambler because they also adapt the same risk but there's really huge difference on the way how people execute each activities.
But people really tag those long term minded people as investor because we know this is really the best option to do especially if the asset is well known to bring something good to people who have good patience and proven to bring good profits base on its historical movement.
But for sure there well be good transition that going to happen and those traders would choose to HODL Bitcoin and forget about trading it especially if they encounter huge disaster on their trades and lost lots of money with it.
Maybe the ideal words to use to avoid these arguments is to attarch long or short term to the investors. If one is keeping his coins for a very long time he could be referred to as long term investors while others could be short term investors. I assume that many Bitcoiners don't like calling traders investors since they don't have interest in hodling just like most Bitcoiners do.
Anyway, I don't see trades as gamblers because they do thesame job as forex traders. And I don't think people call forex traders gamblers. But they share thesame features with gambling which is high risks.