Too high humidity will cause unnecessary condensation in cooling fin (coldest parts of blower), when condensation kicks-in, icing/geling will occur minimally even with drainage system to clear extra condensate. With icing/gelling occuring, of course dirt, glime and dust will trap in "fins" even thou filter is there. This is where choking begin as non-liquid substance accumulation in blower system.
Other effect of condensation in pipes (cool) due to high humidity result in mould/wet insulator. Mould will tend to growth in wet & cool area aka wet trunking. Growing mould in your room can be Bad for health thou.
Yes, in AC room can be very dry and low humidity but cannot be help as I mention above which why AC system are make to reduce humidity in process of cooling.
IMHO, Adding humidifer adds to electric bills plus extra burden to AC systems and compromise health in mould growing also. Yes, all above mention situation can be rectified but at a cost of money and health.