Every time your currency changes, some financial institution applies a rate at which the money is converted. Unsurprisingly, built in to that rate is a fairly fat margin for them. That they should make profit is of course fine, but they also build in a margin "against fluctuation" despite executing plenty of transactions the other way around where they benefit from said fluctuation. I confess I am always amazed (given the advancement in poker understanding in general in recent years) who widely neglected the subject of currency exchange is. For someone with no understanding, I would encourage you to walk into a Bureau de Change with £100 and ask for dollars. Walk round the block, go back with the dollars and ask for £. When you get considerably less than £100 for it, you will start to understand how bad it is. It wouldn't take many such walks round the block before your £100 turned to dust.
So, for poker players with multiple poker accounts in $, MB allows you to move money conversion rate-free whenever you go skint on one site, win on another and care to move money across. This assumes you have your MB account in USD!
Stars are in a class of their own with the functionality to have 4 currencies within your cashier. This means you can play in $ and withdraw in £ if you like at spot rate but this is very much the exception and not the rule.
So with a USD MB account, you can stop paying so many currency charges whilst you move money around, you simply pay once at the point of withdrawal. In the old days, you could win $10k playing poker, withdraw it to your bank for a holiday to Vegas and then take the ££ to an FX Bureau to receive about $9k (the effect of the Bureau + bank charges) Poker players are renowned for being tight on fractions of a percent, but are often oblivious to this massive scalping, which is all very puzzling. Now, you could get a MB debit card in USD which means $10k poker profit = $10k for you to access in USA. There may be some usage charges on the card, but these are waived at VIP level.
Ah yes, VIP level. Tighter spreads, higher limits, points on transactions, where you can get cashback or use to get ipads etc for free. Withdrawal fees refunded. The debit card is free and you can open a second (and eventually third) currency. So now you would have £ € and $ covered. Great for holidays, keep a few notes lying around and then start taking out €500/day locally from ATMs as well as using it at points of sale. And last but not least, you can be an absolute boss in one of these:
