How do you define entire account exactly?
If a trader is bad and has just $100 to risk on FX (and ONLY $100 and no more) and that he risks the whole thing on one trade today that's gambling not trading and it's exceptionally bad, I agree 100%.
Now if the trader has $100 in his FX account but has a fantastic job and mean to cable $1000 each month (WHEN NEEDED and just when needed) to his FX account, then it does not matter he is bets that the whole $100 using a 400:1 leverage or 4000:1 leverage, it will not make a darn difference in his trading results/profits.
Actually this is exactly what I did 5 years, when I started trading on the Currency Market (I traded the SP 500 futures ). I opened my account with exactly $100 and opened a 200:1 leverage commerce. My brother saw this and told me that I was crazy to do that, way too much leverage that he explained.
Of course it seems that way at first glance. What he did understand of course is that I had more than $50,000 to alloe to the Currency Market market, but $100 at a time when and IF needed.
But hey only try it, open two miniature demo accounts.
Let's presume that mini-account 1 gives you $50,000 to perform but account #2 provides you $100 to trade with.
Okay, place your trades generally in both accounts and wager just $100 every time. Of course should you lose $100 (account # 2, leverage utilized 100:1) simply open another miniature demo account and repeat this operation as many times as required.
After 1000 trades in this way, you will notice that you have the SAME EXACT profits in both accounts, not a penny less, though you're alloing 100% of your cash to every trade in account #2 and just 0.0002% of your cash in account #1!!!
That is what the majority of traders have a hard undertanding.