You are correct that SBD is not being printed anymore (at the time or your question and now). At the time of your question, the maximum percentage that SBD could be in relation to Steem was 5%. Once the market cap of SBD reached 5% of the market cap of Steem, then it stopped printing. Now after Hardfork 20 the limit has been increased to 10%. The amount of SBD printed decreased in a linear fashion once the percentage hit 8% and stopped entirely when it reached 10%.
That doesn't mean the SBD that was already printed is removed. That would be like saying that is the USA decides to stop printing more dollar bills that no dollar bills exist anymore. There's still there, but no new ones are being created at this time.
The only time SBD are destroyed is through the conversion mechanism internal to Steem. The process takes 3.5 days and at the end of that period, the SBD is converted to Steem at the current rate. Other than that, the SBD continues to exist. People still have SBD in their accounts and are still able to transfer those SBD to bidbots or anyone else.
If you want to use bidbots that only take SBD and you don't have any, you can buy some with Steem using the internal market https://steemit.com/market. You pay Steem and get SBD from someone who wants Steem. The rate varies as people place orders to buy or sell, so you can potentially get better ratios some days than others.
tl;dr Yes, SBD stops printing, but those in existence are still there and able to be traded or used however the owner sees fit.
The fact that SBD is not being printed anymore doesn't mean that SBD does not exist on the blockchain. It's usefulness still very much exits, and its need is evident.
The thing is that SBD is technically a smart contract which exists as a 'debt instrument' that is payable/redeemable in Steem tokens.
Steem token is the native currency of the Steem blockchain and is meant to be vested back in the blockchain through the process of powering up. In a hypothetical scenario, if all the Steem were to be powered up, then there would be a problem of liquidity within the Steem ecosystem. This is why we need SBD to maintain liquidity as well stability of price (since its bottom threshold is pegged to one dollar worth of Steem).
Note: To understand better why SBD is not being temporarily printed you can take a look here: https://musing.io/q/dorislanda/f32s4e4tx?r=profile-hashcash
The fact that SBD is currently not being printed doesn't deem it useless. On the contrary, users will still use it just the same they did before the change in print rates.
They will basically keep existing because SBD is not extincted, it's only hibernating because of the current situations of the steemit platform, the market and the current price. SBD will be printed soon, besides STEEM can always be traded for SBD, vice versa