You have said it yourself that trading doesn't guarantee regular profits. Matter of fact, I would say, trading doesn't guarantee profits itself.
So considering that many people lose money while trading it wouldn't make much of a sense if we quit our day job for trading.
Surely some people do make money out of trading but even in that case, why not have your stable job and continue trading part time.
Investment is risky, trading is more dangerous so except if you are as either an investor or a trader who already made millions or billions of dollar from investment or trading, and already took it to fiat currency, cash, bought real estates and some luxury things, you should never quit your job.
It's because profit today from either investment or trading, can turn to loss in future if you continue your investment or trading, and don't cash it out all or partially.
It's addictive to continue with trading or investment and because they're both very risky, you can lose your money quickly with them too. Quitting your job, and getting loss later, your life will become very hard.
Besides that, at times when you have spare cash with you, you'll feel like to invest it all which is called as compulsive buying.
I have suffered from it and this can cause your bank balance to vanish. This is another reason to not leave the job when you are making profits.
To avoid this, we must set a strict budget for trading and try not to cross it buying everything we can when the market falls.