Although I do not like their free cent promotion but I do not agree with your suggestion as if they give free $5 each month, it will be so easy to be abused because it has no requirement at all.
Imagine if they do as what you suggest, hundreds or maybe thousands of people will create so many accounts in order to get the free $5 then withdraw it as there is no minimum withdrawal amount + no withdrawal fee IIRC.
I think the better option is to have daily faucet with bigger amount like 5-10 cents so players can play few bets after claiming the faucet.
If they run giveaways, they must have ability to catch multiple accounts on their website. As a casino, I think they don't have issue to detect multiple accounts like some casinos have faucets for users too.
If they run giveaway, they must write clear rules about how to claim it, like multiple accounts are prohibited. I believe all casinos have Terms of Service against multiple accounts especially if those accounts are used to claim faucets, giveaways, cheat the system.