Generic warnings are easy to ignore, so here are the numbers.
Example 1, deposit match. A casino offers a 100% bonus on an AUD 100 deposit with a 30x wagering requirement. Nominal turnover required is AUD 3,000. If Spaceman contributes only 10% toward wagering, a common setting for crash games, every AUD 1 staked counts as just AUD 0.10. Real turnover needed to release the bonus becomes AUD 30,000. At an effective house edge of 3.5%, the expected cost of generating that turnover is around AUD 1,050, vastly more than the AUD 100 bonus. If contribution is set to 0%, Spaceman play does not advance the wagering requirement at all.
Example 2, turnover-for-bonus promotion. Some operators reverse the structure: wager a total of AUD 250 on Spaceman to unlock an AUD 50 cash bonus credited by support, usually with a 7-day window and a verified account requirement. This model is easier to evaluate, because the required turnover is fixed and disclosed. Expected cost of AUD 250 of turnover at 96.50% RTP is roughly AUD 8.75, which compares favourably with the AUD 50 reward, provided the bonus is genuinely withdrawable and you meet the deadline.
The lesson is not "never take a bonus". It is "calculate the required turnover, then multiply it by the house edge before deciding".
For balance, research on promotional credits is less one-sided than marketing rhetoric suggests: