Pips per trade strips out lot size and account size to measure the raw edge of a strategy. A strategy averaging +3 pips per trade with 60% win rate is positive expectancy; a strategy averaging -2 pips per trade will bleed out regardless of how much capital is behind it.
The problem with raw pips is that it ignores slippage, commission, and swap costs. Net pips per trade (gross pips minus all costs) is the honest figure. Most retail traders who think they are break-even in pips are in fact net-negative once all costs are included.