>>13178357There are many, many good reasons.
- It would be unimaginably expensive and wouldn't bring any benefit for thousands of years, so no one has any interest to do it.
- It would completely and forever ruin the possibility of ever finding traces of extraterrastrial life on Mars by contaminating the environment.
- We lack the technology. No life as we know it is capable of growing on Mars as it currently is. Just because some bacteria can survive in the vacuum of space doesn't mean they're active and growing. Furthermore, even if such a life existed, it never would be enough to make Mars hospitable to mankind. For that, Mars would need an atmosphere, but if Mars had an atmosphere, it would be blown away by the solar winds due to Mars' lack of magnetic field, so terraforming Mars requires reigniting its magnetic field, and we can't do that.
Overall, what you are suggesting is completely irrealistic.