It sounds like your getting confused with maximum leverage available on account and the actual leverage used on a trade.
Just because you have an account with a maximum 500:1 leverage, you can still only use 1:10 or less, or any variation up to a maximum of 500:1.
With respect to this, it makes sense for traders to accept the highest maximum leverage available as this reduces the required margin per trade. I have 50:1 maximum leverage on my account, however I never use more than 10:1 - a big difference. Just because you have the opportunity to use all 500:1, it doesn't mean you have to.