Performance and efficiency.
Any kind of restriction on the intake of a compressor, reduces it's performance. If you create any kind of below atmospheric pressure on the inlet side, that is a pressure drop that has to be recovered. Even taking a 0.1bar drop, you'll typically lose 10% of capacity.
Then there is the issue, of air flow. On the intake side, you have far more airflow to have to dry. You would need a lot of surface area to effectively achieve sufficient drying.