What i never actually got- why do we have to wait for this to happen in the wild ? What prevents us from cultivating connected tissuesamples, and breed the supe

What i never actually got- why do we have to wait for this to happen in the wild ? What prevents us from cultivating connected tissuesamples, and breed the superbugs of the next generation in the lab, so that countermeasures are available when it happens? I know that mutations (virus) and recombinations (exchange of dna between bacteria) are unpreditable - but most of them would remain local - only those infectious enough to be transfered are of interest, in the wild as in the lab.