Earning a living with BTC is like working in a bank that will soon go bankrupt.
There are few reasons why BTC is not reliable for earning:
1. BTC prices vary very fast and can make you rich or bankrupt in a day.
2. Gambling is never edged towards your side. The longer you play, the more you lose.
3. Earning online is not something to be proud of nor will it get you a good profile.
4. Trading is very risky and cloud mining is slow and unreliable.
Will these are some valid reasons you have mentioned here. but these are not only ways to earn money on the web. and Trading is not so risky if you have enough trading knowledge, cloudmining is unreliable but actual mining is very profitable but it needs good capital to start.
but there are lots of more ways to earn bitcoin.
1: Offering your skills and service.
2: Work as a freelancers,
3: work as a web, graphic designer,
4: signature campaigns (earning of this method may low but it is really worth)
5: bloging and creating website, creating faucets and gambling site also a good way.