It does not make bid bot users more money if SBD is $1. The bid bot price is generally close to value of the rewards, making it close to break even for the user, and nearly all of the net value of the reward goes to the bid bot owners and delegators.
SBD being $1 makes it useful as a medium term store of value and currency for transactions neither the payor or payee needs to be concerned about huge volatility where prices can go up or down by 20% in a day or more. It adds value to the platform by making it more useful. Having another token with purely speculative value does not add value, it is redudant.
There are other aspects to it discussed elsewhere but I won't repeat them all here in a little comment.