This allows all new users to start playing and earning with non-phantom cards, the credits will be put into the market ecosystem (to the users) as it is also not enough to buy a booster pack. Buying singles, renting cards, or buying potions are really the only use of the credits. Essentially, Splinterlands is giving 3$ back to the community and market for each new spellbook that would normally just be kept by the company.

$3 barely gets you anything on the market apart from some in-print reward commons or current pack commons. This allows new users to start a collection that can be filled out to start earning more, but requires some real cords to earn anything.

Credits are not transferrable, so they have to be used on the market and if you use them to buy from your own accounts you can be banned, from things I have seen in the past.

I am not sure that bots are the real problem. It seems that bots that have not assets are really the root of the economy decay. If all the automated accounts were turned off, I would suspect that there are times of day that users would struggle to pair with players, not at all times, but it would be harder to maintain the active players at all ratings levels. Such as, you may get paired against others that have a much different rating, more often.

Spending 10$ to get 3$ in credit and grind lots of accounts is not as appealing as spending the 10$ on assets for existing accounts, when you earn nothing if you have nothing or next to it. This will move the botting from spell book farming to owning collections worth enough to get to the higher leagues, which increases the market demand and decreases the supply. It will also require the bot developers to fight harder opponents on average to get better rewards.

It is common for players to fight AI opponents in games. in this case, bots also provide a lot of matches for real players to fight and are limited on capturing rewards by ECR, which scales rather well to prevent more matches resulting in more rewards. This reward system takes that even further and will help snuff out the spellbook farmers.