Try depositing your Steem or SBD to ANY exchange that supposedly trades them...yeah, that might be part of the reason why.
I don't know about you, but any time I notice that a wallet is "under maintenance" on an exchange seemingly more often than not that kind of throws up a red flag, especially when over 90% of the wallets for other cryptos don't ever seem to be down for deposits or withdrawals (and only last hours in the cases where they do, whereas Steem was down for something like 2 or 3 months straight on Poloniex at one point).
Don't Do it on poloneix then. Bittrex is much better
The exchanges cant handle the number of transactions I guess :P
"SBD is currently under maintenance or experiencing wallet/network issues. Deposits and withdrawals will remain disabled until a solution is found, which may require an update from the SBD team. Any updates must be tested and audited before enabling."
That's the message on Poloniex right now lol and has been there for about a week now
Yeah, I know. That place is a joke!