I want to do pip-level back testing on my strategies.
Why? Because, with a 10.000 Euro account with 1:100 leverage one pip cost me 100 USD in EUR/USD market. A move in one minute may very well be too large for my strategy to test my stops. I might want to have tighter stops. And on 1-minute data, it is not necessary possible to test.
Second reason is indicators. Let's take "Forex volume". Forex volume is counted as the amount of moves within the bar. Unless my broker has pip level historical data, I don't see how he calculates this value correctly. Maybe, he has a databas on it, or maybe, he just counts the length on the move or something else from the open, close, high, low data. I want to know that my indicators really show me what I think they show me.