If it's a weekly or a monthly bonus that needs a specific wagering requirement then it's better if someone who is a low roller, shouldn't try to reach that threshold as you said they will probably lose more money than they can get from the bonus and that doesn't really make any sense spending $100 to only get a $20 bonus.
If the bonus is a deposit bonus, then one might try and get together the amount that can be eligible for the bonus and deposit that amount so that they can get some bonus with their deposit that provides them with an opportunity to play more which may create some room for winning.
But in reality there are many casinos that provide weekly or monthly bonuses from the VIP rank and this rank can only be obtained when gamblers can meet the wagering amount requirements that have been determined by the casino.
Anyone can get the bonus, it's just that time will determine when they can get it.
Indeed, all bonuses have requirements and if we think about almost all types of bonuses that can be obtained, we have to spend and be willing to lose some money to get these bonuses.
Yes, a deposit bonus is a bonus that can be obtained only by depositing a certain amount of money, but this type of bonus is very rarely held by casinos.