Why would we buy bitcoins? Because we believe in it as a currency. Personally I'm buying what I can afford each month as I'm certain they're going to rise in value for the halving and should be able to make a nice profit with them.
That would be better rather than earning which is hard at this moment. You will need some skills and some knowledge in different fields to get it and that would take time. Same as me I buy each time I got some spare in my salary.