In the same way that I don't spend a penny with credit cards to get air miles. The rewards are very low, and in most cases people end up spending more than if they were not offered rewards, so, using a mathematical simile, it's EV- for them.
For example in BlockFi you need to spend $1k to get $15 (plus possible bonus). For that I prefer to take the $15 (or $20) and buy Bitcoin directly.
I tend to agree.
If we try to chase all those offers and promotions you end up getting 10 bucks and wasting hours. Sometimes even buying things you don't really need.
Sometimes those promotions may be a good deal. But our time looking for those are worth more than those "cashbacks".
They are similar to airdrops.. not worth in the long run.