There’s no way someone will forgot the most important part on this promotion to be qualified.
It’s more on intentional to censor it because the 5K wager is too high for a 5$ free bet. You will likely lose more than ten folds of that reward just to get a 5K wager even on the lowest house edge games like Plinko.
Only few will be attracted to claim that bonus if they saw immediately the requirements.
Many gambling platforms don't emphasize the wagering requirements for bonuses, and probably do so deliberately in order not to scare away gamblers. Incidentally, the Betfury site states that Plinko has an RTP of 99.02%, which means that the expected loss will be $49 when wagering $5k. With this in mind, that free bet no longer seems like such an attractive offer.
Both of you are absolutely right, almost every casino won't publicly reveal the terms and conditions of a bonus, and even when some managed to do so, they won't state that part which tells what the wager requirement is for those that will be interested to claim the bonus, but some casinos I've previously contact usually do tell what the wager requirement is but am always wondering why then not publicly state that in the terms and conditions so that users don't have contacting just because of that..
But then, I learnt that the reason for this Is because some gamblers don't usually care about finding out this information before claiming the bonus, they go ahead and claim it only to later discover that claiming the bonus was a big mistake.
Like I've always said, casinos don't give anything for free, there can never be a bonus that doesn't have some strings attached, and gamblers must always ensure they are away of every single information patterning to a bonus before claiming it to avoid getting themself into error.