I also do not get why using the leverage is a negative thing as long as you stay within risk norms.
Exposure to force majeure risk. Everybody would use high leverage if it was as easy as setting and forgetting a stoploss order.
Quick example with easy round numbers: with a normal stop level of -1% of the instrument, maybe the worst slippage encountered is say net -1.5%. On 10:1 leverage (conservative by FX/futures standards) that's still a manageable -15% on equity, just a horrible day. If some crazy news hits which completely eliminates liquidity down to -20% of your entry, on that leverage you're looking at -200%: so a $100K balance allocated at 10:1 for a $1M position just became -$100K in the blink of an eye, where the stoploss (which is a market order) finally got executed. Broker will collect. Best case you're with a market-maker like Oanda or FxPro which contractually forgives negative balances (thanks to B-booking), and you're just out 100%, still a very bad day.
ops:Granted, it very rarely happens, and you have to be exposed exactly at the wrong time, but rarely isn't never. With leverage, we do not have the absolute guarantee that we will still be able to trade tomorrow; we're gambling on the improbability of our stops getting executed 20x further from our entry than we anticipated.
(Although when I say leverage, I mean on one's entire net worth, not on the equity which happens to be parked at a given brokerage account to satisfy margin requirements. In the example above if say you're worth $200K, with $100K of that at the broker, net you're now flat broke. No debt at least, but you're now jobless.)