Very valid point! Especially if we are trading Futures. Normally by the time the buy signal is triggered, the stock has already made a long way.
In overall bullish Nifty trend, stock gives handsome returns. Some examples like LT - buy triggered at 1205, ICICIBANK - buy triggered at 839.45, BGREnergy etc.
But in sideways to bearish market, sometimes entries get stuck. In cash, it is not a big problem but in Futures, it sets panic in.
Recently you had similar advice for entry in RCOM for one of the member.