Why do it,because there is long-term investing,mining or the possibility to do other business,including offline?
I believe that when you trade or invest, it's always accompanied by a new learning just as these two things. So, if you are an investor, then in the long run you will have to learn about trading. And if you are a simple trader then you'll get to learn more about investing.
We're not stagnant and we're going to learn more things in finance such as the crypto market and these things of investing and trading. If you are going to ask why trading and not the others? because we've got the basics of it as buy and sell.
Anything that we do has a learning process and along the way, we can unlock more knowledge. If we start as an investor, there is a trading mechanics when we are buying a coin. Same goes when we sell later on. It's also true that when we start as a trader we can learn investing eventually because there are instances that we decided to wait for the price to recover before we trade.
It's okay to stay on trading despite of it, as long as you are doing good and maybe adding, or switching more can only cause of our collapse. Trading has the basics of buy and sell but what about investing? Also trading can still become complicated later on but this is also highly rewarding, which can be the reason on why some prefers it.