For one thing,mistakes are made all the time. If people didn't question the status quo, we would still be using a model of the galaxy that had the earth at its center. Scientific experiments have to be testable and reproducible...anything can happen once.
Secondly, not everyone is entirely truthful. In history, the side that wins tends to write their version of the truth, and finding out what really happened can be difficult. Being a skeptic is, I think, necessary if one wants to be truly informed.
Doubt allows us to think of alternatives and make contingencies. Without it, if people put all of their eggs in one basket and fail, the results can be disastrous. With proper planning, results can still yield positive rewards.
Chambers's Dictionary defines scepticism as:
that condition in which mind is before it has arrived at conclusive opinion: doubt: the doctrine that no facts can be certainly known: general disposition to doubt.
Of these different shades of meaning, the first one implies that scepticism is a condition that is natural response of people to all new facts presented to them. The alternative to this scepticism will be blind faith when we accept all that is said without questioning. Surely that does not appear to be a very good alternative.
In general all new ideas that come our way are likely to be a mixture of good and bad, right and wrong, and the like. It is for the receiver to use caution and judgment in separating grain from the chaff.
Of course this is not supporting the general disposition to doubt, which is a sign of reluctance to examine and accept any new ideas rather than a careful attempt to evaluate each new idea on its merit.