If a person is practical, well what you say is correct, that's why there are others who enter this industry because they lack knowledge, they have the mindset to buy Bitcoin mining rigs thinking that they will just wait for profit in bitcoin without thinking much about it.
But in today's time, I would really prefer to buy bitcoin because compared to mining it is too much of a hassle unlike buying after it is up to us whether we hold or short term trading.
In early days, it was easy to mine Bitcoin (even people mine bitcoin on laptops) but now a days you need expensive mining devices that consumes too much power. Bitcoin mining is for specialised groups that have the capability to setup large and complex mining rigs. Although everyone is free to join Bitcoin mining, one must calculate how much he can return he will get after setting up his solo mining rig. I never jumped into Bitcoin mining since I know I wont earn much from it.