This is only a good method if you're aiming for long term, if you put your money that you'll be needing soon then it's not a good choice to buy BTC. Cause if you want to a quick flip that you could profit instant then buy and store is not recommendable.
You are right. Keep buying Bitcoin any time and never caring about the price are okay for long-term investment, but it is not effective way for a shot term investment or trading. Not each person buys Bitcoin for a long-term holding, some people just buy Bitcoin for short holding or even trade Bitcoin weekly or monthly.